Mechanical Computing Systems

ABSTRACT

Systems and methods are disclosed for creating mechanical computing mechanisms and Turing-complete systems which include combinatorial logic and sequential logic, and which are energy-efficient.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.14/986,568 filed 2015 Dec. 31, and incorporated herein by reference.

FEDERALLY SPONSORED RESEARCH

Not applicable.

SEQUENCE LISTING OR PROGRAM

Not applicable.

FIELD OF INVENTION

The present invention relates to the field of computer technology orcomputer systems relating to general purpose devices that can beprogrammed to carry out a set of arithmetic or logical operations. Morespecifically, the present invention is directed to mechanical computing,wherein a mechanical computer is built from mechanical components ratherthan electronic components.

BACKGROUND OF THE INVENTION

Methods for mechanical computation are well-known in the prior art.(Svoboda, “Computing Mechanisms and Linkages,” New York, DoverPublications, 1965; Bradley, “Mechanical Computing inMicroelectromechanical Systems (MEMS),” AIR FORCE INSTITUTE OFTECHNOLOGY, AFIT/GE/ENG/03-04, Ohio, 2003; Sharma, Ram et al.,“Mechanical Logic Devices and Circuits,” 14th National Conference onMachines and Mechanisms (NaCoMM-09), 2009) However, while the earliestexample of a Turing-complete design is probably Babbage's AnalyticalEngine, which was described in 1837 (although never built), the vastmajority of previous proposals for mechanical computing are notTuring-complete systems. Rather, they are either special-purpose devicesnot intended to address general-purpose computing at all, or they arepartial systems or mechanisms, lacking crucial capabilities which wouldallow them to provide Turing-complete systems. For example, with respectto partial systems or mechanisms, known examples include logic gatesbuilt from custom parts, kits, or even toys like Lego. Note thatmechanical logic gates alone, even universal ones, do not by themselvespermit Turing-complete computing; some memory means is also required.Turing-complete computing requires a means for combinatorial logic, aswell as a means for sequential logic.

The mechanical computing literature also includes molecular-scaleimplementations of various computational components (again, often notTuring-complete systems), including (Drexler, “Nanosystems: MolecularMachinery, Manufacturing, and Computation,” New York, John Wiley & Sons,1992; Hall, “Nanocomputers and Reversible Logic,” Nanotechnology, 1994;Heinrich, Lutz et al., “Molecule Cascades,” Science, 2002; Remon,Ferreira et al., “Reversible molecular logic: a photophysical example ofa Feynman gate,” Chemphyschem, 12, 2009; Orbach, Remacle et al., “Logicreversibility and thermodynamic irreversibility demonstrated byDNAzyme-based Toffoli and Fredkin logic gates,” PNAS, 52, 2012; Roy,Sethi et al., “All-Optical Reversible Logic Gates with OpticallyControlled Bacteriorhodopsin Protein-Coated Microresonators,” Advancesin Optical Technologies, 2012).

While previous designs for mechanical computing vary greatly, previousproposals capable of Turing-complete computing (as opposed tolimited-purpose devices) tend to reply upon a substantial number ofbasic parts (or “primitives”) including various types of gears, linearmotion shafts and bearings, springs (or other energy-storing means,e.g., some designs use rubber bands), detents, ratchets and pawls, orother mechanisms which have the potential to be energy-dissipative, aswell as increasing the complexity of the device. Note that such designsrequire these various primitives to function properly; they are notoptional.

That the use of many types of basic parts in a mechanical system cancomplicate design, manufacture, and assembly, as well as potentiallyreducing reliability, is obvious. Reducing the complexity of mechanismsis a common inventive goal.

Note also that many of the mechanisms used in previous proposals formechanical computing generate substantial friction. Removing suchmechanisms would have benefits beyond reducing device complexity,including reduced energy expenditure. However, judged by the prevalenceof friction-generating mechanisms in mechanical computing systems, it isdifficult to design around this issue.

Perhaps less evident than friction are other modes of energydissipation, including vibrations, which may, e.g., create heat, orgenerate acoustic radiation. For example, ratchets and pawls, detents,or other mechanisms which involve the relatively uncontrolled impact ofone piece of a mechanism upon another can lead to energy-dissipatingvibrations, and so the removal of these types of mechanisms would alsohave benefit.

Waste heat is a well-known issue for computational systems, electronicor mechanical, which dissipate far more energy per bit operation than isrequired in theory. In theory, computations can be performed where theenergy dissipated is only ln(2) k_(B)T per irreversible bit operation.This is called the Landauer Limit (Landauer, “Irreversibility and HeatGeneration in the Computing Process,” IBM Journal of Research andDevelopment, 1961) and has been confirmed experimentally (Berut,Arakelyan et al., “Experimental verification of Landauer's principlelinking information and thermodynamics,” Nature, 7388, Nature PublishingGroup, 2012).

Note that the Landauer Limit only applies to irreversible operations.Reversible operations can, in theory, dissipate zero energy. Whileconventional computers are generally not built upon reversible hardware,reversible computing has been studied for decades (Landauer,“Irreversibility and Heat Generation in the Computing Process,” IBMJournal of Research and Development, 1961; Bennett, “The ThermodynamicsOf Computation,” International Journal of Theoretical Physics, 12, 1973;“Logical reversibility of computation,” IBM Journal of Research andDevelopment, 6, 1973; Toffoli, “Technical ReportMIT/LCS/TM-151—Reversible Computing,” Automata, Languages andProgramming, Seventh Colloquium, Noordwijkerhout, Netherlands, SpringerVerlag, 1980; Toffoli and Fredkin, “Conservative Computing,”International Jounral of Theoretical Physics, 3/4, 1982; Bennett andLandauer, “The Fundamental Physical Limits of Computation,” ScientificAmerican, 1985; Feynman, “Quantum Mechanical Computers,” Foundations ofPhysics, 6, 1986). For a general overview of reversible computing from asoftware perspective, see (Perumalla, “Introduction to ReversibleComputing,” CRC Press, 2014).

Whether reversible or irreversible, novel designs for mechanicalcomputational systems that have the potential to reduce devicecomplexity (along with the associated design, manufacturing and assemblycosts) and use less energy per bit operation than existing designs,would be quite useful. Not being subject to the Landauer Limit,reversible designs have the potential to ultimately use the leastenergy. However, existing computing systems use energy so far in excessof the Landauer Limit that even irreversible designs could greatlyimprove upon the state of the art.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the invention include mechanical computing mechanisms andcomputational systems which have lower energy dissipation, a smallernumber of basic parts, and other advantages over previous systems.Multiple embodiments are disclosed including mechanical link logic,mechanical flexure logic, and mechanical cable logic, along with designparadigms (including both mechanical designs, principles, and a novelclassification system which categorizes systems as Types 1 through 4)that teach how to apply the general principles to other embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, reference isnow made to the following descriptions taken in conjunction with theaccompanying drawings, in which:

FIG. 1 depicts a side view of a molecular rotary joint.

FIG. 2 depicts a side view of a four-bar linkage.

FIG. 3 depicts a top view of a mechanism which can serve as the basisfor a NAND or AND gate.

FIG. 4 depicts a top view of a mechanism which can serve as the basisfor a NOR, NAND, AND, or OR gate.

FIG. 5 depicts a top view of a XOR gate.

FIG. 6 depicts a top view of a Fredkin gate.

FIG. 7 depicts a top view of a co-planar lock in the (0,0) state.

FIG. 8 depicts a top view of a co-planar lock in the (1,0) state.

FIG. 9 depicts a top view of an alternate embodiment of a co-planar lockin the (0,0) state.

FIG. 10 depicts a top view of an alternate embodiment of a co-planarlock in the (1,0) state

FIG. 11 depicts a ¾ view of a non-co-planar lock in the (0,0) state.

FIG. 12 depicts a top view of a non-co-planar lock in the (0,0) state.

FIG. 13 depicts a ¾ view of a non-co-planar lock in the (1,0) state.

FIG. 14 depicts a top view of a non-co-planar lock in the (1,0) state.

FIG. 15 depicts a ¾ view of a non-co-planar lock in the (0,1) state.

FIG. 16 depicts a top view of a non-co-planar lock in the (0,1) state.

FIG. 17 depicts a top view of a balance with an input of 0.

FIG. 18 depicts a top view of a balance with an input of 1 with ananchor at the top.

FIG. 19 depicts a top view of a balance with an input of 1 with ananchor at the bottom.

FIG. 20 depicts a top view of a binary double balance with inputs (1,0).

FIG. 21 depicts a top view of a binary double balance with inputs (1,1).

FIG. 22 depicts a top view of a switch gate.

FIG. 23 depicts a top view of a lock and balance-based NAND gate.

FIG. 24 depicts a top view of a lock and balance-based Fredkin gate.

FIG. 25 depicts a top view of a shift register cell in its blank state.

FIG. 26 depicts a top view of a shift register cell after input has beenprovided but before a clock signal is set to high.

FIG. 27 depicts a top view of a shift register cell after input has beenprovided and a clock signal has been set to high.

FIG. 28a depicts a top view of the left half of a two-cellshift-register.

FIG. 28b depicts a top view of the right half of a two-cellshift-register.

FIG. 29 depicts a top view of a canceling group.

FIG. 30 depicts a top view of a flexure-based lock.

FIG. 31 depicts a top view of an MCL pulley and associated mechanisms.

FIG. 32 depicts a side view of an MCL pulley and associated mechanisms.

FIG. 33a -FIG. 33c depict top views of various states of one embodimentof an MCL lock.

FIG. 34 depicts a ¾ view of a knob which can be used to create a lock.

FIG. 35 depicts a ¾ view of two knobs forming a lock in the (0,0) state.

FIG. 36 depicts a ¾ view of a lock in the (0,1) state.

FIG. 37 depicts a ¾ view of a lock in the (1,0) state.

FIG. 38 depicts a top view of an MCL oval.

FIG. 39 depicts a top view of an MCL balance in the (0,0) state.

FIG. 40 depicts a top view of an MCL balance in the (0,1) state.

FIG. 41 depicts a top view of an MCL balance in the (1,0) state.

FIG. 42 depicts a top view of an MCL balance in the (1,0) state afteractuation.

DETAILED DESCRIPTION OF THE INVENTION Definitions

The following definitions are used herein:

“Anchor block” means one or more rigid structures to which basic partsor higher-level assemblies can be attached, and which may also serve asheat sinks. Note that even when written in the singular, there may bemore than one anchor block, as design needs dictate. The shape of ananchor block can be arbitrary (“block” should not be taken to mean thatthe structure is necessarily rectangular, or any simple shape). Ananchor block can be made from any appropriate material, not limited to,but including any of the materials suggested herein from which basicparts could be made. An anchor block is assumed to be present as neededwhether explicitly stated or not.

“Anchored” means attached to an anchor block, or otherwise renderedimmobile with respect to other relevant basic parts or mechanisms.Anchoring may be permanent or conditional (e.g., depending on datainputs or clock signals), and a conditionally anchored part may bereferred to by its relevant conditional state (i.e., if the part isunanchored in a given situation, it may be referred to as unanchored,and vice versa).

“Atomically-precise” means where the identity and position of each atomin a structure are specified by design. Structures such asnaturally-occurring or bulk-manufactured crystals or quasicrystals,having surface irregularities, impurities, holes, dislocations or otherimperfections, are not atomically-precise. Atomically-precise can, butdoes not have to, include knowledge of isotopic composition.

A “balance” is a structure which transmits movement through one side orroute of a mechanism versus another. Balances can be used, e.g., toperform computations and to route data. A balance may have any number ofinputs and outputs, some of which may be anchored, or conditionallyanchored (as when connected to a lock). The word “balance” and formsthereof may also be used in its traditional sense (e.g., equal masses orforces ‘balance’ each other) as context dictates.

A “basic part” is a fundamental building block, or primitive, of amechanism or computational system. For example, the basic parts of MLLare links and rotary joints, the basic parts of MFL are links andflexures, and the basic parts of MCL are cables, pulleys, and knobs.“Basic part” is synonymous with “primitive,” and the distinction betweena basic part and a mechanism is that basic parts are, at least in theirsimplest implementations (e.g., a pulley is a basic part because it canbe monolithic, but some implementations of a pulley could require anaxle as a separate part), not obviously logically divisible into smallerparts.

A “cable” is a flexible structure used to transmit tensile forces, e.g.,directly, or via pulleys.

“Coaxial” refers to rotary joints which share the same axis of rotation.The term may also be applied to the analogous concept in co-planarmechanisms which have multiple joints that share common arcs ofmovement.

“Computing system” and forms thereof including “computational system”means a system for carrying out general-purpose computations. Suchsystems are Turing-complete. Devices only capable of solving a single,or a limited class of, problems, such as planimeters, harmonicsynthesizers or analyzers, equation solvers, function generators, anddifferential analyzers, are not capable of general-purpose computing,and are therefore not “computing systems.” Power sources, motors, clocksignal generators, or other components ancillary to Turing-completecomputational means are not part of a computing system. Different typesof computational systems may be interfaced. For example, an MLL systemcould take its input, provide its output, or otherwise interact withother mechanical or electronic computing components, systems, sensors,or data sources, although such a system would only constitute an MLLcomputational system if the MLL components themselves provideTuring-complete computational means.

“Co-planar” refers to a mechanism that moves in one or more parallelplanes. The term is used to differentiate essentially flat (butpotentially multi-layer) implementations of mechanisms from those whichutilize movement in non-parallel planes. The distinction is largely oneof convenience for naming and visualization, as the mechanisms describedherein can be constructed in either a co-planar or non-co-planar manner.

“Data link” means a link that aids in transferring data, from onelocation to another. A data link may be simply called a “link” whencontext makes the meaning clear.

“Dry switching” as applied to the mechanical computational componentsdescribed herein means that no force is applied to mechanisms that arenot free to move in some way.

A “flexure” is a type of bearing which allows movement through bendingof a material, rather than sliding or rolling.

“Fork” means a branch in a line allowing one data link to be coupled tomore than one other data link. A fork can, e.g., allow the copying ofone input/output to multiple links or lines.

“Input” means the data, for example encoded by physical position,supplied to a mechanism, e.g., for purposes of storing the data inmemory, transmitting the data elsewhere, performing combinatorial logicon the data, or actuating the mechanism (e.g., via a clock signal). Fora variety of reasons, including that the input to one mechanism can bethe output from another, that some mechanisms use the same data as bothinputs and outputs (e.g., a circular shift register or other mechanismswith a feedback loop), and because some embodiments permitreversibility, there may be little distinction between “inputs” and“outputs,” the use of one term or the other being more for didacticpurposes. Therefore, regardless of which term is used, both are assumedto apply if appropriate in a given context.

“Line” means a sequence of connected data links. Also called a “dataline.”

“Link” means a rigid structure or body connected to one or more rotaryjoints.

A “lock” is a structure with a plurality of inputs where one or more ofthe inputs being set to some pre-defined range of values results in theother inputs being locked. For example, in a two-input lock, uponsetting one of the inputs to a non-zero value, the other input is lockeduntil the non-zero input is returned to zero. In a two-input binarylock, the non-zero value being set would typically be 1, but the lockmechanism may engage well before the input actually reaches 1 (e.g., aninput of 0.1 on one input may be sufficient to lock the other input).

“Logic gate” includes traditionally-irreversible gates such as AND,CNOT, NAND, NOT, OR, NOR, XNOR, XOR, reversible gates such as Fredkinand Toffoli gates, or other mechanisms which provide combinatorial logic(e.g., reversible implementations of traditionally-irreversible gates,or special-purpose logic gates).

“MCL” stands for Mechanical Cable Logic, a paradigm for creatingcomputational systems and mechanisms thereof, using cables, knobs, andpulleys.

A “mechanism” is a combination of basic parts forming an assembly of alevel of complexity between that of a basic part and a computationalsystem. For example, in MLL, lines, locks, balances, logic gates, andshift registers are all components, as are any sub-assemblies whichinclude more than one basic part. By virtue of being basic parts, linksand rotary joints, or any other basic parts, are not mechanisms.

“MFL” stands for Mechanical Flexure Logic, a paradigm for creatingcomputational systems and mechanisms thereof, using links and flexures.

“MLL” stands for Mechanical Linkage Logic, a paradigm for creatingcomputational systems and mechanisms thereof, using links and rotaryjoints. Note that as the first and most extensively describedembodiment, details are provided for MLL that are not necessarilyrepeated for MFL, MCL, or other embodiments. For example, clocking isdescribed extensively in the context of MLL, but not other embodiments.Due to the analogous logical and mechanical nature of the variousembodiments presented, given the teachings herein, it will be apparenthow to apply information presented for one embodiment to otherembodiments.

“Not-coaxial” refers to two or more rotary joints which do not share thesame axis of rotation, or the analogous concept in co-planar mechanisms.

“Output” means the data, for example encoded by physical position,provided by a mechanism. See “Input” for additional detail and commentson the interchangeability of the two terms.

A “pulley” is a mechanism which facilitates the routing of, and/ortransmission of forces by, one or more cables. Traditionally, pulleysrotate as the cable moves, but this is not necessary, e.g., a cablecould slide over a pulley's surface if the energy dissipation incurredwas suitably low. Pulleys may be anchored or unanchored. Unanchoredpulleys may be free to move as dictated by their attached cables, or mayhave their movements constrained by a track, groove, or other guidingmeans.

“Rotary joint” means one or more connections between rigid bodies thatallow rotational motion about an axis. Rotary joints may be anchored orunanchored.

“Support link” means a link that provides physical support or kinematicrestraint for other links.

“Turing-complete” has its standard meaning as used in the field ofcomputer science, with the caveat that, since real-world systems havebounded memory, time, and other parameters, such practical limitationsare acknowledged to exist, and so the term “Turing-complete,” whenapplied to an actual system, may be taken to include such limitations(resulting in what may be more precisely called a “linear boundedautomata”).

Introduction

Herein it is first shown that a mechanical computational system can bedesigned solely from two basic parts: links, and rotary joints (plus ananchor block to which these basic parts can be affixed; this will besubsequently assumed and not necessarily mentioned each time), using adesign paradigm referred to as Mechanical Linkage Logic (“MLL”).Subsequently, the paradigms of MLL are generalized to show other ways inwhich simple and efficient mechanical computing systems can be designed,such as Mechanical Flexure Logic (“MFL”) and Mechanical Cable Logic(“MCL”) (any of which could also be used in combination). Part of thisgeneralization also includes the description of a novel classificationsystem based on ways in which mechanical computing systems can dissipateenergy.

These new paradigms can simplify the design and construction ofmechanical computing mechanisms and systems, and reduce or eliminatemajor sources of energy dissipation, such as friction and vibration,while still operating at useful computational speeds. Such computationalsystems can also be designed to operate reversibly. These, and otherfactors, offer various benefits over previously-proposed computingsystems.

Embodiments of the invention provide all the mechanisms necessary tocreate Turing-complete computational systems. For example, using MLL,this includes lines, logic gates, locks, and balances, and more complexmechanisms such as shift registers, each requiring no basic parts otherthan links and rotary joints. Other embodiments (e.g., MFL and MCL)provide analogous basic parts and mechanisms to also permit the creationof Turing-complete computational systems.

Energy-Efficient Mechanical Computing

As discussed herein, mechanical computing systems can dissipate energyin several ways, including friction (including drag caused by thermalmovement at the atomic level), and vibrations, which can be caused notonly by running a mechanical system fast enough to excite its resonantfrequencies (something which can be avoided by controlling clock speed),but by part-to-part impacts or relatively unconstrained releases ofenergy. Examples of such part-to-part impacts and relativelyuncontrolled releases of energy include the snapping motions of ratchetand pawl mechanisms, and detents.

Given these issues, four categories are defined for mechanical computingdevices:

Type 1: Devices which store potential energy (e.g., in a spring) andwhich then release this energy in a manner unconstrained by thecomputational degrees of freedom. Devices which use ratchets and pawls,or detents, are examples of a Type 1 device, as the release of storedenergy by the ratchet and pawl or detent are assumedly not tied to thecomputational degrees of freedom. In such a device, if, e.g., a ratchetand pawl were present, while the snapping motion of the pawl might occurwith a periodicity controlled by a clock system, the energy release ofthat snapping motion would not be tied to the clock frequency. Rather,the speed of the energy release would be a function of, e.g., the forceapplied to, and the mass of, the pawl, regardless of the overallcomputational speed of the system. The resulting collision of the pawlwith the ratchet could generate vibrations which waste energy.

Type 2: Devices which store potential energy, and then release thisenergy in a manner controlled by the computational degrees of freedom.For example, in the MLL systems described herein, if a spring was to beplaced between links in a line, as the system drove the line back andforth, the spring would compress and decompress. This compression anddecompression would take place gradually, at the frequency imposed by asystem clock. The spring would not be allowed to snap an unconstrainedpart into place at a speed which, from the perspective of the systemclock, is arbitrary. Rather, the movement of the spring and attachedparts is governed by the computational degrees of freedom. Note thatalso in the above scenario, the spring is part of a continuous linkage,and so no collision of parts occurs like when a ratchet is impacted byits pawl. This can also help reduce dissipated energy. And, even if partcollisions do occur (e.g., see the descriptions of knobs in MCLsystems), since the speed with which such contacts occur can be coupledto the computational degrees of freedom, it is possible to choose speedswhich do not dissipate unacceptable amounts of energy (and in fact, bydriving such impacts with the system clock, which preferably uses a sinewave-like signal, even a relatively fast switching speed can result invery low part velocities at the moment of impact).

Type 3: Devices which do not store more than trivial amounts ofpotential energy, but have parts with non-trivial unconstrained degreesof freedom. For example, depending on the implementation, systems couldbe created using MLL where, due to one or more locks being in the blank(0,0) position, connected links are free to move in an essentiallyrandom manner due to thermal noise, system vibrations, or other causes.Among other issues, such unconstrained movement can result in having toexpend energy to periodically set mechanisms to a known state to ensurereliable operation. (Note that such situations can be avoided withproperly designed systems, and this is presented as exemplary only).

Type 4: Devices which do not store more than trivial amounts ofpotential energy, and have no more than trivial unconstrained degrees offreedom. For example, a properly designed MLL system where all movementis, directly or indirectly, coupled to data inputs and/or the systemclock. No components are allowed to freely “float” as might a linkconnected only to a lock in the blank state. With respect to defining“trivial” unconstrained degrees of freedom, this means those which occurin a small enough portion of the overall system (e.g., one particulartype of mechanism has this issue, but the mechanism is rare in theoverall system), or those that occur infrequently enough, that they donot materially affect overall energy dissipation. An example ofinfrequently-occurring unconstrained degrees of freedom would be whensome system mechanisms have temporarily unconstrained degrees of freedomduring an initialization or reset process. Such processes might only beneeded very infrequently compared to standard computation operations,and so would contribute very little to a system's energy dissipation.With respect to defining “trivial” when used in reference to potentialenergy, note that all mechanical systems will store some potentialenergy. For example, in theory, even very rigid links deform slightlywhen force is applied to them. Assuming no permanent deformation, theythus technically store potential energy. Such unavoidable potentialenergy storage is considered trivial. The point of Type 3 and Type 4systems is the avoidance of systems which purposefully store potentialenergy for later release, such as in a system with springs, where thosesprings and their potential energy are required for the system tofunction properly.

Note that lack of substantial deformation is not the only way to achievea Type 3 or Type 4 system. Flexures may have substantial deformation,but can be designed to store trivial amounts of either total or netpotential energy, as is explained herein. These categories are generallyordered by their potential for energy efficiency, with Type 1 devicesbeing the least efficient, and Type 4 devices being the most efficient.That being said, the energy efficiency of specific systems depends onimplementation details. A Type 2 system could be less efficient than aType 3 system. A poor implementation could make any system energyinefficient. Due to the use of ratchets and pawls, detents, springs, orother mechanisms which store and then release potential energy in amanner not tied to computational degrees of freedom, all pre-existingTuring-complete systems for mechanical computing can be categorized asType 1.

Mechanical Linkage Logic

An MLL system is built from various basic parts or primitives. In theembodiments described, these are rotary joints and links, which togetherform mechanical linkages. Mounted on an anchor block, rotary joints andlinks can be used to create higher-order mechanisms such as datatransmission lines, locks, and balances. Still higher order mechanisms,including logic gates (both reversible and irreversible) and shiftregisters can be created by combining locks and balances, or implementedmore directly using links and rotary joints. This suffices to build acomplete computational system.

To demonstrate this, using only links and rotary joints, the design ofdata lines, logic gates, locks, and balances is explained. Subsequently,using some of these mechanisms, the building of a shift register isdescribed. Shift registers are simple, yet when combined with one ormore logic gates which provide for universal combinatorial logic,contain all the fundamental elements required for computation. If thebasic parts can build a shift register and appropriate logic gates, itfollows that an entire computational system can be built.

Note that most of the mechanisms described are tailored towards binarycomputational systems. As a result, most links will move between twoallowed positions. Some exceptions exist however, such as designs where,for example, when one input is 1, the mechanism drives one or more otherinputs “backwards” (uses of words such as “forward,” backward” and otherdirections being didactic conventions only, since no particulardirections need be used in actual mechanisms, nor do such directionsneed to be consistent from one mechanism to the next). In other words,given a two bit input that starts at (0,0), an input of 1 could causethe mechanism to end up in a state such as (1,−1) or (1,−0.5) ratherthan (1,0). As long as the system is designed to correctly handle suchkinematics, this need not be a problem. Also, links internal to theimplementation of various mechanisms may move between more than twoallowed positions, even if the inputs and outputs are still binary.Binary is used for exemplary purposes because it is the most common typeof computational system used in conventional computers. Ternary,quaternary, or other non-binary computational systems could obviously bebuilt using the teachings herein.

The mechanisms herein were frequently simulated or diagrammed withLinkage v3 (free from www.linkagesimulator.com), Autodesk Inventor2015/2016, or for molecular models, HyperChem, GROMACS, or Gaussian.Many of the figures herein represent sub-assemblies taken out of thecontext of a complete computational system. As a result, they are notnecessarily functional as shown. For example, a given mechanism may notbeing fully constrained as depicted because, in a complete system, themechanism would attach to other components to satisfy missingconstraints, or would attach to some manner of actuation (e.g., a clocksignal). Realistic routing of data has sometimes been omitted in favorof, e.g., straight lines, for clarity. Ancillary support structures,such as anchor blocks, or links which serve only to provide rigidity(“support links”), are generally omitted.

Some diagrams depict parts within mechanisms which are not basic partsof MLL. The most prevalent example of this is the use of linear slidesin Linkage models. This is a programmatic convenience because somemethod of driving inputs is required to run a simulation in Linkage. Inan actual system, linear slides would be replaced with, e.g.,connections to appropriate inputs/outputs, such as data lines or clocksignals. Note that the kinematic solver used by Linkage v3 has noconcept of clock cycles, so it cannot drive various inputs sequentially.And, Linkage, and other programs, may fail on valid mechanisms simplybecause the solver cannot compute the kinematics correctly. Due tothese, and other, caveats, the figures herein should not be taken ascomplete, working mechanisms, but rather as didactic examples which,given the teachings herein, can be readily adapted to create workingmechanisms, and combined to create complete computational systems.

Rotary Joints

Friction in a rotary joint can be made smaller and smaller as the sizeof the rotary joint gets smaller and smaller. At the molecular scale, arotary joint comprising two atoms rotating around a single bond arguablyhas zero contact area, and various rotary joints which rotate around theaxis of single chemical bonds have been analyzed and found to have verylittle friction. For example, carbon-carbon single bonds, using carbonatoms mounted on diamond supports, are one way to create a rotary jointthat provides rotation with very little energy dissipation.

FIG. 1 depicts a molecular model of one possible implementation of arotary joint being used to hold a rotating member. An upper supportstructure 101 and lower support structure 102, which would be connectedto, e.g., an anchor block, in a complete device, are used to connect aset of upper and lower bonds, along the same axis of rotation, to arotating member 103. The upper bonds include upper carbon-carbon singlebond 104, upper carbon-carbon single bond 105, and upper carbon-carbontriple bond 106. The lower bonds include lower top carbon-carbon singlebond 107, lower bottom carbon-carbon single bond 108, and lowercarbon-carbon triple bond 109

The rotary joint is bonded to the support structures by several oxygenatoms, including upper oxygen atom 110 and lower oxygen atom 111. Therotating member 103 as depicted is a roughly circular slab of diamond,but this is representative only, as are the other structures. Therotating member could be a link, a flywheel (e.g., to generate a clocksignal), or anything else that needs to rotate, in any shape.

Molecular dynamics simulations indicate that, with or without theacetylenic units exemplified by upper carbon atoms and triple bond 106and lower carbon atoms and triple bond 109, this structure allowsrotation with remarkably little drag. However, interposing an acetylenicunit between the surrounding single bonds further reduces the energydissipation of such a rotary joint.

Given this example it will be obvious that varied implementations,including other molecular structures, could provide the same type ofmechanism. For example, with small modifications to the model depictedin FIG. 1, the oxygen atoms exemplified by oxygen atom 110 and oxygenatom 111, might be replaced with nitrogen, or another element with anappropriate valence, bond strength, and steric properties. Similarly,carbon could be replaced with silicon or other appropriate elements. Or,entirely different structures could be used, including carbon nanotubesor other structures, preferably those which can stiffly holdmolecular-scale rotary joints.

Additionally, such a rotary joint does not need to consist of only asingle bond or pair (e.g., upper and lower) of bonds. For example, inlarger implementations, the rotary joint could be replaced with a veejewel bearing, a rolling element bearing, nested fullerenes (e.g.,carbon nanotubes), or any one of many ways known to allow rotation,preferably with low friction. Also, multiple co-axial rotary joints canbe used to create a stronger joint (e.g., using a structure similar tothe interdigitated design of a door hinge). And, at the molecule scale,adding additional rotary joints on the same rotational axis couldfurther reduce the rotational barrier if appropriate attention is paidto symmetry. Note that while a rotary joint can be formed using onebond, device strength and stiffness can benefit from a rotating partbeing held on two sides, as depicted in FIG. 1, and/or using multiplebonds, such as in the “door hinge” example. With respect tomolecular-scale embodiments, for ease of description, rotary joints maybe referred to as rotating about a single bond, although in some casesit would be more precise to say that multiple bonds may be used to forma single axis of rotation for the overall rotary joint.

The magnitude of the rotational barriers, the torque required toovercome them, the length of the lever arms (e.g., links), and the timeto rotate the link through the necessary range of the rotary joint (andhow far that range is) all depend on the design of a particular system.As an example, molecular dynamics simulations show that the energyrequired to rotate a link connected to a molecular rotary joint throughone radian at a speed of 1×10E9 radians/sec and a temperature of 180Kcan be below 1×10E-25 J. The Landauer Limit is 1.72×10E-21 J at 180K.This number is so far above the 1×10E-25 J figure for a one radianrotation of a link around a rotary joint that even mechanisms that usemany rotary joints to perform a single bit operation could do so underthe Landauer Limit. Further, it is expected that viscous drag fromrotary joints, and energy loss from other vibrational modes, willrapidly decrease as operating temperature decreases due to phononsbecoming frozen out.

Links

At their most basic, links are stiff, rod-like structures, although someimplementations may have different or substantially more complex shapes.Most of the analysis herein which requires estimations of values such aslink mass, resonant frequencies, and heat conduction, assume a link iscomposed of a diamond rod approximately 20 nm in length and 0.5-0.7 nmin diameter. However, links could be larger, or smaller, or completelydifferent in shape (as seen in the non-co-planar lock examples).

One of the smallest ways to implement a link would be to use a singlecovalent bond as a link. For example, there are many molecules whichhave more than one possible configuration, and the transition betweenconfigurations (“conformers”) could constitute the movement of a link.One specific example is cyclohexane, which has several possibleconformations, including two chair conformations, the basic boatconformation, and the twist boat conformation. Switching betweendifferent conformations can occur through bond rotation (although otherchanges, such as changes in bond angle or torsion, may also be presentand used), similar to that in the previously-described rotary joint, andresults in the movement of one or more of the atoms in the structure.

The ability of such molecular conformational changes to propagate overrelatively long distances and through complex networks is known to existin biology, where it is termed “conformational spread”. (Bray and Duke,“Conformational spread: the propagation of allosteric states in largemultiprotein complexes,” Annu Rev Biophys Biomol Struct, 2004), and itwill be apparent that synthetic systems could be designed that work onthe same principles as larger linkages, but using only a single bond asa link. Such designs could allow link lengths in the angstrom range.

Regardless of the exact implementation of links and rotary joints, oneof the basic tasks in a computational system is to move data from placeto place. The exemplary systems described use links connected by rotaryjoints to move data. While many types of linkages would work, includinglinkages that provide true straight-line movement, 4-bar linkages arefrequently used as an exemplary manner of precisely constraining linkmovement. FIG. 2 depicts a side view of such a 4-bar linkage (note thatthese are sometimes called 3-bar linkages, since the support structuremay or may not be considered an additional bar), comprising an anchorblock 205, left support link 202, right support link 207, and data link204, wherein the lower end of the left support link 202 is connected tothe left side of the anchor block 205 by left anchored rotary joint 203and the lower end of the right support link 207 is connected to theright side of the anchor block 205 by right anchored rotary joint 206,and the upper end of the left support link 202 is connected to the leftside of the data link 204 by upper left rotary joint 201 and the upperend of the right support link 207 is connected to the right side of thedata link 204 by upper right rotary joint 208. Left anchored rotaryjoint 203 and right anchored rotary joint 206 are prevented from movingwith respect to each other by the anchor block 205. Data link 204transmits the movement of one support link to another support link. Theleft support link 202 and right support link 207 are shown shifted tothe left. The left-leaning support links put the data link 204 in aposition to the left of the left anchored rotary joint 203 and rightanchored rotary joint 206. Arbitrarily, this left position can be called“0” or “low”, while if the left support link 202 and right support link207 were leaning to the right, that position could be called “1” or“high.” This provides a basis for a binary system of data storage andtransfer.

It will be apparent, even in the absence of the anchored rotary jointsymbol, that left anchored rotary joint 203 and right anchored rotaryjoint 206 are anchored rotary joints because they terminate on anchorblock 205. In subsequent figures the anchor block may not be explicitlyshown. Rather, the diagrammatic convention is often adopted whereunfixed rotary joints are depicted as a circle at the intersection ofmultiple links (which are generally represented as straight lines orbars, although some may have more complex shapes), while fixed oranchored rotary joints are depicted as a circle and a triangle withshort diagonal lines at its base. In other figures, generally to reducecomplexity, some of these conventions may be changed or eliminated. Thefigure descriptions and context will make it obvious how such diagramsare to be interpreted.

As has already been described, information can be transmitted along thelength of a single data link. However, more complex transmission androuting of data can be useful. One data link can be connected to anynumber of other data links to continue the transmission of data. Datatransmission can continue in a straight line across additional supportlinks (while effectively just a longer data link, it may be useful toinclude additional support links to increase stiffness), or can changedirection at rotary joints, at whatever angle and in whatever planedesired. And, one link can connect to multiple other links not onlysequentially, but also through forking structures, effectively copyingthe data for use in multiple locations. This provides considerableflexibility in routing data.

Data transmission may occur in both directions. Movement of a first datalink causes a second data link to move, and movement of the second datalink causes the first data link to move. By this means every data linkin the chain is tied to its neighbors. All the data links in a chain,which can be of some significant length, can be made to share a commonmovement, a property that can be used to share a single binary valuealong the entire length of the chain. A set of connected links is calleda line.

Scale

MLL could be implemented using basic parts of virtually any sizedesired. For example, at macroscopic scales, conventional machining or3D printing could be used, with, e.g., vee jewel bearings orrolling-element bearings for rotary joints and conventional beams orrods for links. At a smaller scale, e.g., 3D printing, lithography-basedtechniques, or any of the other well-known ways in which NEMS/MEMSdevices can be manufactured, could be used to create devices withmechanisms in the nanometer to micron range. At an even smaller scale,MLL mechanisms could be molecular-scale. Due to the higher operationalfrequencies and reduced energy dissipation which tend to be afforded bysmaller parts, MLL systems would preferably be implemented at thesmallest scales feasible (while taking into account factors such asperformance requirements and budget). For this reason, while most of theteachings herein are scale-independent, estimations of energydissipation focus on an exemplary molecular-scale embodiment.

Molecular bearings, gears, and rotors have been studied boththeoretically and experimentally, and representative literature includes(Han, Globus et al., “Molecular dynamics simulations of carbonnanotube-based gears,” Nanotechnology, 1997; Kottas, Clarke et al.,“Artificial Molecular Rotors,” Chem. Rev., 2005; Khuong, Dang et al.,“Rotational dynamics in a crystalline molecular gyroscope byvariable-temperature 13C NMR, 2H NMR, X-ray diffraction, and force fieldcalculations,” J Am Chem Soc, 4, 2007; Frantz, Baldridge et al.,“Application of Structural Principles to the Design of Triptycene-BasedMolecular Gears with Parallel Axes,” CHIMIA International Journal forChemistry, 4, 2009; Wang, Liu et al., “Molecular Rotors Observed byScanning Tunneling Microscopy,” Three-Dimensional Nanoarchitectures,2011; Isobe, Hitosugi et al., “Molecular bearings of finite carbonnanotubes and fullerenes in ensemble rolling motion,” Chemical Science,3, 2013; Carter, Weinberg et al., “Rotary Nanotube Bearing Structure andMethods for Manufacturing and Using the Same,” U.S. Pat. No. 9,150,405,2015).

Molecular motors, while not necessarily required to drive MLL systems,are commonplace enough now that entire books and conferences are devotedto the topic. (Joachim and Rapenne, “Single Molecular Machines andMotors: Proceedings of the 1st International Symposium on SingleMolecular Machines and Motors,” Springer, 2013; Credi, Silvi et al.,“Molecular Machines and Motors,” Topics in Current Chemistry, Springer,2014)

Additionally, molecular-scale computing, in various forms (generally notTuring-complete), already exists. (Heinrich, Lutz et al., “MoleculeCascades,” Science, 2002; Reif, “Mechanical Computing: The ComputationalComplexity of Physical Devices,” Encyclopedia of Complexity and SystemScience, Springer-Verlag, 2009; Remon, Ferreira et al., “Reversiblemolecular logic: a photophysical example of a Feynman gate,”Chemphyschem, 12, 2009; Orbach, Remacle et al., “Logic reversibility andthermodynamic irreversibility demonstrated by DNAzyme-based Toffoli andFredkin logic gates,” PNAS, 52, 2012; Roy, Sethi et al., “All-OpticalReversible Logic Gates with Optically Controlled BacteriorhodopsinProtein-Coated Microresonators,” Advances in Optical Technologies,2012).

In addition to other techniques present in the literature,molecular-scale MLL mechanisms and computational systems could becreated using, e.g., molecular manufacturing using mechanosynthesis, orassembly of properly functionalized molecules using atomic forcemicroscopy-type equipment. Conventional chemistry or self-assembly(including DNA origami-type techniques) may also be a feasible route formanufacturing molecular-scale MLL mechanisms. Given the very limitednumber of basic parts required (e.g., links and rotary joints in MLL)for the presented embodiments, synthesis and assembly of the necessarybasic parts and mechanisms is in many ways simpler than the complexitiesof manufacturing a conventional electronic computer or than implementingprevious proposals for mechanical computing.

Energy Dissipation

As noted, an entire MLL system can be constructed with nothing but linksand rotary joints. Since, particularly at the molecular-scale, there isvery little energy loss from rotation around a well-designed rotaryjoint, a complete computational system can be designed which dissipatesvery little energy. Additional MLL design paradigms (e.g., torque andmass balancing to reduce or prevent acoustic radiation) are alsodiscussed herein, and these can help reduce energy dissipation evenfurther. Beyond the physical design of the computational system,operating conditions can also affect energy dissipation. For example, ifan MLL system is operated in a vacuum, acceleration and deceleration oflinks takes place smoothly, and the applied forces are small enough thatdeformation of basic parts contributes negligible energy dissipation,energy dissipation may be reduced further.

The design of MLL mechanisms, and their interaction with the clockingsystem, may also affect energy dissipation. For example, MLL systems canbe designed such that, by using clock phases appropriately, force is notapplied to mechanisms that are not free to move (e.g., such a systemdoes not try to move a locked mechanism without first unlocking it).This is the MLL version of “dry switching,” a term normally used in thefield of relays to indicate that switches have no voltage across themwhen changing state, but herein will be used in the context of MLL. Notethat while it is a major novel finding of MLL that completecomputational systems can be designed with nothing beyond links androtary joints, MLL systems may incorporate, or interface with,additional components. For example, it is described herein how cams andcam followers are one way to generate clock signals. However, eventhough cams and cam followers can be designed (as is explained herein)to have minimal energy dissipation, such mechanisms are ancillary to,not actually part of, MLL. Motors or other ways of powering the movementof MLL systems are another example of a function that may be coupled toan MLL system, but are not considered part of MLL, and the same could besaid for, for example, input/output interfaces which bridge, e.g., MLLand electronic systems or non-MLL mechanical systems.

Any mechanical system can dissipate substantial energy if run fastenough to excite internal mechanical resonances. To keep powerdissipation as low as possible, proper design can avoid low frequencyvibrational modes being coupled to the clock, and the remainingvibrational modes can be computed and avoided by picking a speed ofoperation slow enough to avoid exciting them, as well as a clockingwaveform that minimizes their excitation. In a molecular-scalemechanical system such resonant frequencies can be in the gigahertzrange, and the limits they impose on switching speed can therefore becorrespondingly high.

The switching speed of an MLL system will, just as in electroniccomputers, be determined by one or more clocks which produce clocksignals. If the frequency spectrum of a clock signal has a component ofits energy at or above the resonant frequencies of the mechanisms towhich it is attached, then a greater fraction of the clock energy couldbe dissipated than is necessary.

In an MLL system, changes in a clock signal are preferably gradual so asnot to generate higher frequency components. For example, the gradualchanges inherent in a sine wave-like transition between 0 and 1(potentially with flat areas at 0 and 1 between transitions to allow fornon-perfect synchronization of mechanisms between different clockphases) allow a clock signal to avoid placing greater strain on systemmechanisms than necessary as parts accelerate and decelerate moreuniformly than if, e.g., a square wave, was used.

There are many ways of generating clock signals. One way of generating agradually-changing clock signal is to use a spinning mass whoserotational motion is converted into linear or quasi-linear motion. Thisis, conceptually, the equivalent of a flywheel and crank, and such adevice can be made with only links and rotary joints. Some embodimentsof MLL systems may couple to other methods of generating clock signals,such as spring and mass systems, or cams and cam followers, which aredescribed herein.

Several possible sources of energy dissipation were analyzed, includingstress induced thermal disequilibrium, and acoustic radiation. Thesewere not the primary limiting factors in operating frequency, at leastfor the exemplary systems analyzed (e.g., molecular-scale, diamond-basedsystems). Mechanical resonances and inertia are the primary limits toswitching speed for these systems.

While thermal equilibration turns out not to be a limiting factor forthe exemplary systems analyzed, in some situations it could be, and oneobjective when seeking to minimize energy dissipation could be tooperate mechanisms isothermally. For this reason, short thermalequilibration times can be desirable. To achieve this, the basic partsof the system are preferably well-coupled to one or more thermalreservoirs. For example, links are generally bonded to a rotary jointwhich is bonded to an anchor block, or to rotary joints that bond toother links, which are in turn bonded to an anchor block. While theexact path length can vary based on the implementation, this tends tokeep the path from any link to an anchor block, which can serve as athermal reservoir, short.

Note that diamond is used as an exemplary anchor block material (and mayalso be used for basic parts), for among other reasons, due to its highstiffness (Young's Modulus of about 1000 Gpa). Diamond also has goodheat conduction, which can be over 2000 W/mK in natural diamond, andhigher in defect-free and isotopically purified diamond (a principlewhich applies to other materials as well). Many other materials could beused, for both anchor blocks and basic parts, although high stiffnesswould be preferred for various reasons, including raising the frequencyof resonant vibrations, and good heat conduction would be preferred iffast thermal equilibration is desired. Other exemplary materials includeCarbyne (Young's Modulus of 32,100 GPa), various Fullerenes (e.g.,carbon nanotubes can have Young's Moduli of over 1000 GPa, thermalconductivity of 3180-3500 W/mK or higher), Silicon Carbide (Young'sModulus of 450 GPa), and Silicon (Young's Modulus of 130-185 GPa,thermal conductivity of 148 W/mK). Note that these values areapproximate, and generally represent values measured at 300K (roomtemperature). The values may vary substantially depending on amaterial's atomic structure, purity, isotopic composition, size andshape, and temperature. For example, while Silicon's thermalconductivity is 148 W/mK at 300K, it can exceed 3000 W/mK attemperatures around 20K.

Further, note that MLL systems need not be composed of only one type ofmaterial. Various materials each have different pros and cons, includingnot only bulk properties such as stiffness, thermal conductivity, andthermal expansion, but at the molecular scale, the strength ofindividual bonds may become important, as may be the exact size ofvarious basic parts and their inter-atomic spacing (e.g., so that theymesh properly with other basic parts, among other concerns). Given this,MLL systems may use a variety of different materials.

The estimated thermal equilibration time of one exemplarymolecular-scale embodiment using diamond links about 20 nm in length is˜0.54 ps. Given this, even a few nanoseconds of thermal equilibrationmakes the energy dissipated due to thermal disequilibrium essentially 0.Therefore, thermal equilibration time is not the limiting factor inswitching time for such an embodiment.

In theory, a reversible operation can be carried out with 0 energy,while irreversible operations result in the dissipation of ln(2) kBT ofheat (˜3×10-21 J at room temperature) per bit erased, regardless of thehardware's efficiency (the Landauer Limit). To reduce the energydissipation of a program running on a conventional (irreversible)computer, the logic elements of the hardware might be redesigned todissipate less energy during the computational process. This couldresult in a significant improvement in energy efficiency because aconventional computer dissipates much more than ln(2) kBT per erasedbit. In fact, even when executing instructions that erase no bits atall, a conventional computer dissipates much more than ln(2) kBT peroperation. As a consequence, it is possible to reduce the energydissipation of a conventional computer without paying any attention toreversibility.

However, if the energy efficiency of a computer is improved to the pointthat the Landauer Limit becomes significant, reversibility becomesimportant, as it allows computations to be carried out under theLandauer Limit. Consequently, MLL mechanisms are designed to allowreversibility, although both reversible and irreversible computationalsystems can be implemented using MLL. Note that reversibility can occurat several levels. For example, an individual Fredkin gate isreversible. However, reversibility may also be implemented at higherlevels, such as when using a retractile cascade to uncompute a series ofprevious computations. Such techniques are well-known in the literature,along with appropriate clocking schemes such as Bennett Clocking andLandauer Clocking.

Conventional Logic Gates

Links and rotary joints not only serve as the basic parts for movingdata from place to place, but also form the basis for logic gates. Animportant finding of MLL is that any logic gate, reversible orirreversible, can be implemented with only links and rotary joints,affixed to an anchor block to hold them in place (and which may alsoserve as a thermal sink).

For example, FIG. 3 shows a mechanism that can serve as both an AND anda NAND gate. Anchor 301 and linear slide 302 serves as the first inputto the gate, connecting to rotary joint 306. Anchor 303 and linear slide304 serves as the second input to the gate, connecting to rotary joint307. Anchored rotary joints 305 and 309, plus unanchored rotary joints306, 307, 308, 310 and 311 are connected via the appropriate links. ANDoutput 310 and NAND output 311 provide for the use of the gate as an ANDor NAND gate. The functioning of this gate is as follows. If linearslide 302 pushes on rotary joint 306 (an input of “1”, whereas nomovement of the linear slide would be an input of 0) and linear slide304 pushes on rotary joint 307, the effect will be to drive AND output310 forward, producing an output of “1.” If either of the inputs (orboth) are 0, AND output 310 ends up in the same position it started,producing an output of “0.” This reproduces the truth table expected ofan AND gate.

Since a NAND gate is an AND gate with inverted output, the samemechanism can be used as a NAND gate by reading NAND output 311 insteadof AND output 310, assuming that, since NAND output 311 moves in theopposite direction of AND output 310, no movement at NAND output 311represents an output of “1” and movement to the left represents a “0”.Of course, for use only as an AND gate, NAND output 311 need not bepresent. And, for use only as a NAND gate, the AND output 310 can beignored. The two are combined for illustrative purposes; they would notnecessarily be so combined in actual use. Since NAND is known to be auniversal gate (meaning, all other gates can be created with theappropriate combination of NAND gates), this mechanism alone wouldsuffice to create any combinatorial logic. However, it may be moreefficient to construct other types of gates directly, rather thanthrough the combination of NAND gates, and to demonstrate other types ofgates, including an alternate embodiments of the NAND gate, additionallogic gates are subsequently described.

FIG. 4 shows a NOR gate made with only links and rotary joints. Input 1comprises linear slide anchor 401 and is connected via a rotary joint toinverter 405. Input 2 comprises linear slide anchor 403 and linear slide404 and is connected via a rotary joint to inverter 406. As in all suchfigures, the linear slides are present as a diagrammatic or programmaticconvenience and should be taken to represent some appropriate connectionwhen these individual mechanisms are combined into a higher-levelassembly. Inverters 405 and 406 invert a leftward signal to a rightwardsignal and vice-versa and connect via rotary joints to upper rightportion of the mechanism 407, and lower right portion of the mechanism408, respectively. Due to the inverters, when either of the inputspushes to the right, the movement gets inverted into a leftward motionin the upper right portion of the mechanism 407 and the lower rightportion of the mechanism 408. The position of output 409 replicates theexpected truth table, with the illustrated position representing a “1”and the position where the output moves to the left representing a “0”.While other implementations are possible, this gate was shows themodular nature of the mechanisms. A NOR gate is equivalent to an ANDgate with both inputs inverted. The upper right portion of the mechanism407 and the lower right portion of the mechanism 408 therefore show analternate implementation of an AND gate, with an inverter attached toeach input to instead create a NOR gate. Removing the inverters andconnecting the inputs directly to the appropriate locations in the upperand lower right portion of the mechanism would result in an AND gate.Also, as was shown in FIG. 3, this mechanism could then also serve as aNAND gate by inverting the output of the AND gate. Finally, if theinverters are left in place, but the output inverted, the NOR gatebecomes an OR gate.

Finally, FIG. 5 shows an XOR gate implemented using only links androtary joints. Input 1 comprises anchored rotary joint 501 and linearslide 502, while input 2 comprises anchored rotary joint 504 and linearslide 503. Input 1 and input 2 are coupled to output 505 via a series oflinks, anchored rotary joints, and unanchored rotary joints. Themovement, or lack thereof, at output 505 replicates the expected truthtable for XOR.

The foregoing demonstrates that any logic gate can be directlyimplemented using only links and rotary joints. Note that by carryingthe input data forward along with the expected output of a logic gate sothat no data is lost in the computation, logic gates which aretraditionally considered irreversible can be made reversible. There arealso well-known logic gates which are inherently reversible, such as theToffoli gate and Fredkin gate, which can also be implemented in manyways using MLL.

Reversible Logic Gates

FIG. 6 shows a Fredkin gate (also called a CSWAP gate), a well-knownuniversal reversible gate. The three inputs to the gate 601, 602 and 603are connected, via a series of links, anchored rotary joints, andunanchored rotary joints, to outputs 604, 605 and 606. It may be ofinterest to note that this particular implementation of a Fredkin gateis composed of three XOR gates, and an AND gate, plus some forked datalines used to replicate data so that it can be used at more than oneplace within the gate. This demonstrates not only more sophisticatedrouting of data than the previous gates, but that reversible logic canbe constructed from irreversible logic. A Fredkin gate does not eraseany data and so need not be subject to the Landauer Limit.

Given the foregoing logic gate examples, it will be obvious that anytype of logic gate necessary for implementing a complete general-purposecomputing system, reversible or irreversible, can be implemented withinthe design paradigms of MLL, using only links and rotary joints. Notethat each of the foregoing logic gate examples are co-planar mechanisms.This means that they operate in one or more parallel planes, withmovement occurring parallel to the plane of the image. One of theadvantages to co-planar designs is that they are easy to represent onpaper, to provide the reader with an intuitive understanding of how suchmechanisms work. This is not the only way to implement logic gates, orany MLL mechanism, and mechanisms that move in more than one plane arealso discussed herein. Also note that in the co-planar mechanisms,hidden or dotted lines are generally not used to show which links arebehind which other links. This is because it largely does not matter. Inmost cases, a given link could be on top of, or below, some other link,and the function of the mechanism would not be affected, subject toconsiderations such as not having links bump into each other duringmovement. One may also wish to consider issues such as arranging thelinks in a manner which minimizes the distance to a heat sink, ormaximizes mechanism strength or stiffness, but these exemplary designsare meant to be didactic, not to provide an optimal implementation.Optimized implementations could differ with the requirements of aparticular computational system, including the types of computations tobe performed, the desired computational speed, the desired size or massof the system, the materials from which the mechanisms are made, and theoperating environment (e.g., operating temperatures).

Locks

Various ways in which multiple data links or lines can interact havealready been described. For example, they can share data by tying theirphysical movements to each other around a common rotary joint. And datalinks or lines can provide input/output for a logic gate (not to mentionbeing used inside a logic gate). However, additional methods ofinteraction can be useful in implementing a complete computing system.

Another way multiple links or lines can interact is via a mechanismwhich causes links to interfere with each other's movements. That is,the position of a first link can allow or prevent one or more otherlinks from moving, and vice versa. For example, consider a two-inputmechanism, where each input can be 0 or 1. The design can be such thatwhen both inputs are 0, either input could become 1, but when eitherinput is 1, the other is locked into place and must therefore remain 0.In this example, more than one input cannot become 1 at the same time,although other designs are possible. This mechanism is referred to as alock. It is common for a lock to have inputs and outputs, just like alogic gate. E.g., a 2 input lock has 2 inputs, and can have 0, 1 or 2outputs. Each input line to the lock can either continue as an outputline, or it can terminate at the lock.

One of the uses of a lock is to create a conditional anchor point. Ashas already been explained, a rotary joint can be anchored or notanchored, often depending on whether the rotary joint is affixed to ananchor block. However, affixing a rotary joint to an anchor block is notthe only way to render it immobile. Rather, a rotary joint can beconnected to one or more links which, due to the configuration of theone or more links (whether this configuration is permanent ortransient), does not permit movement of the rotary joint. For example,consider a triangle made of three links. Each link is affixed to the twoother links by rotary joints at each end. If two of these rotary jointsare also connected to an anchor block, even if the third rotary joint isnot connected to an anchor block, it is effectively anchored, as theentire triangle is rigid. None of the triangle's links can move withrespect to each other, or the anchor block. In this simple example,assuming there is no way to change the link configuration, the thirdrotary joint is effectively anchored. There are situations where it isuseful to have a rotary joint sometimes anchored and sometimes notanchored. Locks allow this: The side of the lock that is locked cannotmove, and so as long as it is locked, it can effectively act as ananchor point. The utility of conditional anchor points will be explainedsubsequently. Another useful aspect of some embodiments of locks isthat, for example, a binary lock with two inputs can have three possiblestates: (0,0), also called “blank,” (0,1), and (1,0). The blank statecan be useful in saving state, and allowing reversible computation, ascan be seen herein in the description of how an exemplary shift registercan be implemented.

As with all MLL embodiments, there are multiple ways of implementinglocks using only links and rotary joints. FIG. 7 and FIG. 8 depict atwo-input co-planar lock in two different states. FIG. 7 shows theposition of the lock where both inputs are 0, while FIG. 8 shows theposition of the lock when one of the inputs is 1. Top input 701 andbottom input 702 connect via rotary joints to the top and bottom halvesof the lock, respectively. Each half of the lock comprises a 4-barlinkage, comprising links 703, 705 and 712 on the upper half, and links704, 706, and 713 on the lower half. In addition, four diagonal links707, 708, 710 and 711, hold an additional link 709, which connects tothe two 4-bar linkages via unanchored rotary joints. The functioning ofthe mechanism is as follows: When one of the inputs 701 or 702, movesfrom 0 to 1, the respective 4-bar linkage is moved. The movement of the4-bar linkage, via either links 707 and 710 for the top half, or links708 and 711 for the bottom half, causes the rotation of link 709. Link709, being the same length as links 703, 704, 712, and 713, as well asinitially being at the same angle, allows either of the inputs to assumea value of 1 by pivoting through the same arc that the 4-bar linkagemust follow when moved by an input.

However, once an input has moved either the top or bottom 4-bar linkage,along with link 709, the other 4-bar linkage (and so its associatedinput/output) is no longer free to move. The reason is that link 709 isnow not parallel with, depending on which input was set to 1, links 703and 712, or links 704 and 713. Because of this, the rotation of link 709will not follow that of the second 4-bar linkage, should it try to move.In essence, one of the links (link 705 for the top, if not alreadymoved, or link 706 for the bottom, if not already moved) will be tryingto move through two different arcs at once, resulting in the mechanismlocking. This is essentially a co-planar version of rotary joints beingnot-coaxial (described elsewhere herein), but instead of the rotaryjoint axes changing (which does happen, but these axes were neverco-axial in the literal sense to begin with), the point here is that thearc through which the connected links would move changes. Once one ofthe inputs is set to 1, the only allowed movement is to set that inputback to 0 so that either (but not both simultaneously) sides are againfree to move to the “1” position.

The lock design of FIG. 7 has the property that it locks quickly andunlocks slowly. For example, virtually any movement of one of the inputslocks the other input. And, once an input has been set to 1, locking themechanism, that input must be brought essentially all way back to 0before the lock unlocks. It may be desirable to design locks which havemore gradual locking properties, and this may have advantages includingsmoother changes in entropy (resulting in reduced energy dissipation),reduced maximal force on the mechanisms at a given switching speed, anda reduced time between lock/unlock cycles, since there is less concernthat one input must be allowed to settle to almost exactly 0 before theother input can start to move. The inclusion of springs in connectionsto a lock can also aid in the operation of a lock, as the mechanism canthen be driven as desired even when small positional errors are presentwhich would otherwise lock a mechanism which almost instantly locks whennot exactly in the unlocked position (i.e., at “0”). Another method ofaccomplishing this is to replace link 709 with a spring of the samelength (or add a spring and shorten the link) which has a suitablychosen spring constant. If link 709 is, or incorporates, a very stiffspring, the lock will allow only small positional errors. If link 709is, or incorporates, a softer spring, the lock will allow largerpositional errors.

FIG. 9 and FIG. 10 depict a lock where, due to gradually changing torqueas the mechanism moves from unlocked to locked, the locking action ismore gradual. FIG. 9 shows the lock when inputs 901 and 902, are 0,while FIG. 10 shows the state of the lock after input 901 has been setto 1 while input 902 is still 0. Inputs 901 and 902 are connected to therest of the mechanism via unanchored rotary joints. Note that thesetting of one input to 1 results in driving the other input backwardsslightly in this design. The overall system can be designed to allowthis, or the backwards motion could be kept internal to the mechanism,such as by using springs that absorb such motion rather thantransmitting it directly to other links.

Being made of the same basic parts, all MLL mechanisms tend to sharesimilar concerns. The concepts of sudden versus gradual changes inentropy, limiting maximum forces, and designing mechanisms to allowreduced latency between clock phases, can apply to any MLL mechanism,not just locks.

Non-Co-Planar Mechanisms

Many of the mechanisms herein are of co-planar design. While co-planardesigns are emphasized for clarity of presentation, MLL mechanisms neednot be co-planar. Any MLL mechanisms can be implemented in a mannerwhich is non-co-planar. For example, FIG. 11 depicts a lock, constructedof links and rotary joints, which is not co-planar. Rather, as will besubsequently explained, the rotary joints allow the links to moveperpendicular, rather than parallel, to the face of the Anchor Block.

In FIG. 1 land subsequent views of the same mechanism, link 1101 will bereferred to as Link1, link 1102 as Link2, link 1103 as Link3, space 1104as OpenJoint4, space 1105 as OpenJoint5, space 1106 as OpenJoint6, space1107 as OpenJoint7, rotary joint 1108 as Joint1, rotary joint 1109 asJoint2, rotary joint 1110 as Joint3, rotary joint 1111 as Joint4, andanchor block 1112 as the Anchor Block. The Anchor Block provides anchorpoints for the rotary joints Joint1 and Joint4, which are connected toLink1 and Link2, respectively. Link1 is connected to Link2 by Joint2,and Link3 is connected to Link2 via Joint3. All Joints and Link1, Link2,and Link3 are shown in the unlocked position.

In the unlocked position, which may be referred to as “(0,0)”, the axisof Joint3 is aligned with the axis of Joint1, and the axis of Joint2 isaligned with the axis of Joint4. Joint1 and Joint 3 may thus be referredto as coaxial, as can Joint2 and Joint4. If either Link1 or Link3 wereto pivot, one of their rotary joints would move out of their currentplane, and thus, depending on which link was pivoted, some of the jointswould no longer be coaxial with each other (a condition referred to as“not-coaxial”). The concepts of coaxial and not-coaxial are importantas, in this embodiment, these conditions are what define locked versusunlocked. The reason for this is that in the unlocked position, Link1and Link3 each have an axis about which they might pivot. For Link1,this is the axis defined by Joint1 and Joint 3 when they are coaxial.For Link3, this is the axis defined by Joint2 and Joint4 when they arecoaxial. When these sets of joints are not in the coaxial position, thelack of alignment between the two axes prevents pivoting, as a rigidobject with one degree of freedom cannot simultaneously pivot around twodifferent axes. As a result, when either Joint1 and Joint3 arenot-coaxial, or Joint2 and Joint4 are not-coaxial, the lock is lockedand the only allowed motion is to return to the unlocked position.

Note that technically, virtually any amount of pivoting of Link1 orLink3 would create a locked condition. However, for the purposes ofexplanation, subsequent figures show about 30 degrees of rotation. Thisis arbitrary, and any amount of pivoting which will allow the system toact reliably could be used (as could any other angle, as opposed toperfectly perpendicular to the face of the Anchor Block). Analogouslywith the co-planar lock, if Link 2 were replaced with a spring ofsimilar length, the tolerance of the lock for positional errors in itsinputs could be increased, to the extent thought desirable. It will beobvious given this explanation that if either Link1 or Link3 were topivot a suitable amount, whichever link had not pivoted would then beprevented from doing so until the pivoted link was returned to theunlocked position.

To accomplish this pivoting, OpenJoint4 and OpenJoint6 are connectionpoints where other links could connect to Link3, and OpenJoint5 andOpenJoint7 are connection points where other links could connect toLink1. These other links can serve as inputs to the lock. Link1 andLink3 each have a pair of connections (OpenJoint5 and OpenJoint7, andOpenJoint4 and OpenJoint6, respectively) not to allow four inputs(although that is possible, that is not the intent of this particulardesign), but rather to allow an input line to continue on past the lockif desired. For example, OpenJoint5 may be thought of as a continuationof OpenJoint7 (or vice versa) and OpenJoint4 may be thought of as acontinuation of OpenJoint6 (or vice versa).

FIG. 12 shows a top-view of the same mechanism as FIG. 11, with onlylink 1101 and anchor block 1112 being visible in this view.

FIG. 13 shows the same mechanism as FIG. 11, but in a locked positionthat could be called “(1,0)”. In this state, 1101 has rotated, viarotary joints 1108 and 1110, making rotary joints 1109 and 1111not-coaxial. Because 1109 and 1111 are not-coaxial, 1103 is no longerfree to rotate, hence the locked state. The rotation of 1101 would beaccomplished by other links (not depicted) connected to 1105 and/or1107.

FIG. 14 shows a top view of the state of the mechanism in FIG. 13. Inthis top view, it can be seen that 1101 has pivoted about 30 degreescounterclockwise. 1102 cannot be seen in this view, but would pivot with1101 in this instance, revealing 1103 below it. Note that the directionof rotation is arbitrary. Both clockwise and counterclockwise rotationswould have the same effect of locking the lock. This is true of 1103 aswell.

FIG. 15 shows the same mechanism as FIG. 13, but in a locked positiondue to the rotation of 1103 instead of 1102. This position could becalled “(0,1).” In this state, 1103 has rotated, via rotary joints 1109and 1111, making rotary joints 1108 and 1110 not-coaxial, therebylocking 1101. The rotation of 1103 would be caused by other links (notshown) connected to one or more of the Open Joints, 1104 and 1106, of1103.

FIG. 16 shows a top view of the state of the mechanism in FIG. 15. Inthis top view it can be seen that 1103 has rotated about 30 degreesclockwise, while 1101 is still in its original position. As with 1101,the direction of rotation is arbitrary. Either clockwise orcounterclockwise would allow proper function of the lock, and either orboth could be used.

Given these examples and the principles of MLL, many other designs (forlocks and all other MLL mechanisms) will be obvious. The specificimplementations which work most efficiently may be case-dependent, andthe exemplary embodiments herein are not provided as examples ofoptimized mechanisms, but rather to demonstrate how all elementsnecessary for a generalizable computational system can be created usingonly links and rotary joints, and that even within the constraints ofonly using links and rotary joints, many different logical andmechanical options are available, including virtually any type of logicgates, reversible and irreversible, and mechanisms that largely functionin two dimensions (“co-planar”), or three dimensions (non-co-planar),complete with robust routing of data, at whatever angles are desired.

Balances

Force and motion can be transmitted from one end of a link to the otherend using a rotary joint about which the link pivots. Such a mechanismwill be called a “balance,” since frequently the input is in the centerof a link, and one side moves “up” or “down,” conceptually similar to aclassic pan balance. Of course, the exact movement will depend on theforces applied, the exact mechanism design, and the state of the system.

A simple balance is depicted in two different states in FIG. 17 (showingan input of 0, the linear slide of input 1701 being retracted) and FIG.18 (showing the same mechanism with an input of 1, the linear slide ofinput 1701 being extended). In these figures, input 1701 is connected tothe link 1702 by rotary joint 1703. Upper rotary joint 1704 and lowerrotary joint 1705 connect via links to upper output 1706 and loweroutput 1707, respectively. Upper rotary joint 1704 is anchored in thesedepictions, preventing upper output 1706 from moving, while lower rotaryjoint 1705 is unanchored, allowing lower output 1707 to move if input1701 moves.

FIG. 19 depicts what would happen if upper rotary joint 1704 and lowerrotary joint 1705 were reversed (meaning, if upper rotary joint 1704were unanchored and lower rotary joint 1705 were anchored), given aninput of 1. The output movement would occur at upper output 1706 insteadof lower output 1707. One of the interesting properties of balances isthat they can be designed to conserve the sum of their inputs. In theforegoing example, if the input is 0, the output is 0. If the input is1, the output is 1. This would be true of a simple line as well, butcomplex balances with multiple inputs can be constructed that still sumtheir outputs.

Another advantage to balances is that they can route data differentlydepending on other input. Other input, for example, may control thestate of locks connected to a balance. The locks act as conditionalanchors, routing data down one line or another depending on the state ofthe locks and allowing a balance to function as a switch, or “switchgate.” For example, a single balance with conditional anchors could beput into any of the configurations shown in FIG. 17, FIG. 18, and FIG.19, since the anchor points can be changed (this concept is demonstratedin subsequent figures).

FIG. 20 and FIG. 21 illustrate one way in which balances with multipleinputs can be used to conserve the sum of the inputs, and to route data.Two states of the same mechanism are depicted, which is formed byconnecting two 2-input balances together (a “binary double balance”).Inputs 2001 and 2002 are connected to link 2005 by rotary joints. Link2005 is connected to link 2007 via a rotary joint. Link 2007 connects tolink 2006 via a rotary joint. Link 2006 connects to outputs 2003 and2004 via their respective rotary joints. The fixed length of link 2007causes the sum of the inputs to be conserved. Since link 2007 cannotchange in length, if either input 2001 or 2002 moves, a correspondingmove must take place at output 2003 or 2004. FIG. 20 shows the state ofthe mechanism when input 2001 is 1, and input 2002 is 0. FIG. 21 showsthe state of the mechanism when input 2001 and 2002 are both 1. Notethat the mechanism in these figures (as is frequently the case due tothe complexity of more complete systems and the need for clearillustrations of the basic underlying mechanisms of MLL) is not attachedto other mechanisms as it would be in an actual MLL system. In thisparticular case, without additional constraints this mechanism will notbe reliable. For example, when moving from an input of (0,0) to (1,0),the sum of the outputs must be 1, since the sum of the inputs is 1.However, there is no way to tell if the outputs will be (0,1) or (1,0),or even something like (0.5,0.5). In an actual system, one way ofsolving this problem is with locks. By conditionally locking one of theoutputs, the other output is forced to move in a predictable manner.

Switch Gates

As previously described, balances, in conjunction with locks, are oneway in which a switch gate can be implemented. FIG. 22 shows a switchgate with a top input 2201, a bottom input 2202, and a center input2203. The middle input is connected, via a balance, to top output 2204and bottom output 2205. The top and bottom inputs control whether themiddle input is routed to the top output or the bottom output. Forexample, if top input 2201 is set to 1, then the upper lock to which topinput 2201 is connected, is locked. Since that means that the line goingto top output 2204 cannot move, when an input of 1 is provided at middleinput 2203, the balance to which middle input 2203 is connected mustmove the line which leads to bottom output 2205. The top and bottominput would generally never both be 1 at the same time, so these couldactually be condensed into one input which controls both locks, e.g.,and input of 0 locking the upper lock, and an input of 1 locking thelower lock, or vice-versa.

Binary double balances coupled with locks can also be used as switchgates. Given a binary double-balance, one input is locked permanently,while one input is unlocked permanently and connected to an input(typically a clock). A single line can then be used to switch twocomplementary locks that are connected to the two remaining inputs ofthe double-balance. In essence, the clock input is routed through thedouble balance to one or the other “input” by the single line whichcontrols the two complementary locks. Note that switch gates (and otherMLL mechanisms that have locked states) can be used even when dryswitching is desired. In the case of a switch gate like that in FIG. 22,the clock force is applied via a balance connecting two locks. Since thesystem can be designed so that both locks are never lockedsimultaneously when the clock force is applied, one side is always freeto move. Therefore, the clock force is not directed to an immobilemechanism, but rather to a mechanism that is always conditionally mobilein one direction or the other.

Logic Gates Using Locks and Balances

An interesting property of locks and balances is that they can be usedto create all the traditional logic gates (in addition to othermechanisms), reversible and irreversible. Before describing one way inwhich this can be done, it will facilitate understanding the exemplarylock-based logic gate to discuss an alternate method of providing inputto a mechanism (in this case, a lock). It is typical to think of onebinary input as being a single connection to a line. For example, in thepreviously-described logic gates such as AND, NAND, NOR, and XOR, theselogic gates each took two inputs, often represented as two linearactuators, but what in an actual MLL system would be, e.g., twoconnections to data lines. The Fredkin gate takes three inputs, and sohad three locations where data lines could be connected. Each of theinputs to these exemplary logic gates was binary, meaning, the mechanismwas designed such that one position represented 0, while a secondposition represented 1. Although other implementations are possible,frequently an input of 0 has been represented as no movement occurringat that input, while an input of 1 was represented by some forward orrightward movement.

However, there are other ways to represent input. For example, insteadof a binary input using one connection which provides one of twopossible values (0 or 1), a binary input could consist of twoconnections, one representing 0, and the other representing 1. In thisscenario, one of the connections to an input would always move: The 0line would move if the input was 0, and the 1 line would move if theinput was 1. This is in contrast to 0 being previously represented by nomovement of an input. This strategy of using two lines per binary inputis useful with locks because it allows either value, 0 or 1, to create alocked state. An input of 0 locks one side of the lock, while an inputof 1 locks the other. One use to having both 0 and 1 resulting in alocked state on different sides is that this permits a lock to act astwo different conditional anchor points. This can, for example, be usedto control which side of a balance moves when input is fed into thebalance. The following example shows a mechanism which illustrates howthis property of locks can be combined with balances to create logicgates.

FIG. 23 depicts one way in which a NAND gate can be constructed usinglocks and balances. Clock input 2301 is connected to balance 2302, whichis in turn connected to balance 2303, which is in turn connected tobalance 2304. Via a series of locks and lines, the clock input is thenrouted to balances 2305 and 2306, and finally results in the movement ofupper output 2312 or lower output 2311. Inputs 2307 to 2310 provideinputs to the gate, with four input lines being used to represent twobinary inputs, as previously described. Specifically, input 2307 will bereferred to as “A0” (meaning that it is associated with input “A,” andwill move if the “A” input is 0), input 2308 as “B0,” input 2309 as“A1,” and input 2310 as “B1.” Note that for inputs 2307 to 2310, thereare two inputs each with the same label. This is because the same inputdata is used in two different places within the gate. In reality, thiswould not require two separate inputs for each, but rather one input foreach could be forked using simple rod-like links, or connected to asingle link which provides multiple connection points. The depiction inFIG. 23 was chosen for clarity, not because this need be exactly how themechanism is actually implemented (which is generally true for all themechanisms described herein). The mechanism works as follows: Ifactuated, inputs 2307 to 2310 move the side of the gate to which theyare connected, and lock the gate. In other words, if the input (A,B) is(0,1), the A0 lines will move, and the B1 lines will move. Since A isnot 1, the A1 lines will not move, and since B is not 0, the B0 lineswill not move. Obviously, and input, (0,0), (0,1), (1,0) or (1,1) isallowed. The inputs establish a pattern of which gates are locked andwhich are not. This pattern in turn determines which side of eachbalance is free to move. The clock input then actuates the balances,with the end result being that either bottom output 2311, representing(A NAND B)0, will move, or top output 2312, representing (A NAND B)1,will move. The resulting output generates the NAND truth table:

Inputs Outputs A1 A0 B1 B0 (A NAND B)1 (A NAND B)0 0 1 0 1 1 0 0 1 1 0 10 1 0 0 1 1 0 1 0 1 0 0 1

As has already been mentioned, NAND is a universal gate. Therefore, itfollows from this example that a system of locks and balances could beused to design any other desired logic gates, reversible orirreversible, using combinations of NAND gates. However, this may not bethe most efficient way to implement any desired logic, and similar lockand balance-based mechanisms can be used to implement any other logicgate directly, including AND, OR, NOR, XOR, XNOR, NOT, CNOT, Toffoli andothers.

One implementation of a Fredkin Gate was already described. Locks andbalances can also be used to build a Fredkin gate. A Fredkin gate hasthree inputs and three outputs. The three inputs will be called A, B,and C, and the three outputs X, Y, and Z. Input A always connects toOutput X. If Input A is 0, then Input B connects to Output Y and Input Cconnects to Output Z. If Input A is 1, then Input B connects to Output Zand Input C connects to Output Y. As previously noted, Fredkin gates areuniversal gates, meaning that any logical or arithmetic operation can becomputed with only Fredkin gates. This is not to say that a practicalMLL computing system need be composed solely of Fredkin gates, as thiswould not necessarily be the most efficient configuration for manycomputing tasks. As will be obvious from the teachings herein, manyother types of gates can be implemented using MLL. Fredkin gates areused as one exemplary embodiment because they are both universal andreversible.

FIG. 24 depicts a Fredkin gate made using locks and balances. Due to thecomplexity of the mechanism, a simplified notation is used whereanchored rotary joints are not explicitly shown, but assumed to be onthe unconnected ends of appropriate links. The clock input or signal(actuator not shown, as with all inputs to this mechanism) would beattached to rotary joint 2401. Input for A1, A0, B1, B0, C1 and C0 inputwould be attached to rotary joints 2402, 2403, 2404, 2405, 2406 and2407, respectively. B1, B0, C1 and C0 inputs would also be connected torotary joints 2408, 2409, 2410 and 2411, respectively. The clock signaland inputs are connected via a series of links and locks, and for someoutputs, balances, to X1 output 2412, X0 output 2413, Y1 output 2414, Y0output 2415, Z1 output 2416 and Z0 output 2417. Note that the X1 and X0outputs are not shown on the right side next to the other outputs toreduce figure complexity. In reality, obviously they could be routed toany location desired. Note that links 2418 and 2419 are part of 4-barlinkages, not balances, constraining these links to stay vertical whenmoving. Black triangles 2420 and 2421 exemplify rigid linkages (astraight line is not used to avoid a representation with excessive lineswhich cross each other, and this representation is only diagrammatic;the actual mechanisms could be implemented in many ways).

The blank state is depicted in FIG. 24. Conceptually, from this state,the A, B, and C inputs are set during one clock phase. During asubsequent clock phase, the clock signal connected to rotary joint 2401is set to “1,” which causes the movement of the various balances withinthe mechanism, resulting in the X, Y and Z outputs being set asappropriate. While one straightforward approach to building a systemwould be to use Fredkin gates throughout, and to use three-phaseLandauer Clocking, other approaches are feasible. As will be obviousfrom the various well-known clocking schemes, there may be additionalclock phases, and using Bennet Clocking, the number of clock signalswill depend on the number of steps one desires to allow in a retractilecascade.

Shift Registers

Shift registers can be used as a foundation for implementing sequentiallogic in a computational system. For example, two numbers to be added,subtracted, ANDed or ORed are stored in two shift registers and clockedout into an arithmetic and logic unit consisting of a handful of gates,with the result being sent to the input of a third shift register calledthe accumulator. In reversible digital circuits, a shift register can bedefined as a series of “cells,” each cell having three stable states: 0,1 and blank (b), which can be used to store state information. The cellsare clocked by successive clocks. The output of each cell is connectedto the input of the next cell in the chain. The data stored in the chainis shifted by one position after each clock cycle; data (0,1, or b) atthe input is shifted in while data at the end of the array is shiftedout. Binary clocked shift registers can be implemented using only theclocks and the rotary joints connected by links (creating locks andbalances) previously described. Shift registers are simple, yet whencombined with the appropriate combinatorial logic, contain all thefundamental elements required for a computational system.

A shift register can be built by combining locks and balances, andassuming the presence of a clock system, so that each cell (which mightbe viewed as a flip-flop, and which may also be thought of as a bufferand can be used to synchronize clock phases of different processes byintroducing clock phase delays) of the shift register is related to itsneighbor by virtue of relying upon a preceding or succeeding clockphase, as appropriate. This enables the copying and shifting of datathrough the shift register, rather than deterministically setting thecontents of the entire shift register simultaneously.

FIG. 25, FIG. 26 and FIG. 27 depicts a single cell of a shift register,in three different states. In these figures, the 0 input 2501 isconnected via a rotary joint to one side of lock 2505. The 1 input 2502is connect via a rotary joint to one side of lock 2506. Clock signal2503 (although diagrammed differently to provide a mechanism that ismore complete when standing alone, this would, in an actual system, be aconnection to the clock system), is attached to balance 2504. Locks 2505and 2506 determine which of the outputs 2507 or 2508 move when the clocksignal becomes 1. The lock which contains outputs 2507 and 2588 can bethought of as the output lock for the overall cell, while locks 2505 and2506 are holding area locks. The importance of this concept will becomeclear when connecting multiple cells in series.

FIG. 25 depicts the cell in its blank state, before any input has beenprovided, and while the clock signal is low or 0. FIG. 26 depicts thecell after input 2501 has been set to 1, but before the clock signal hasmoved to high or 1. This results in the locking of lock 2505.

FIG. 27 depicts the mechanism from the previous state once the clocksignal has moved to high. As clock signal 2503 pushes on balance 2504,because lock 2505 is locked, only one side of balance 2504 is free tomove. Thus, the clock signal moving to high is transmitted through lock2506 and to output 2508. Note that the movements between states such asthose illustrated in FIG. 25, FIG. 26 and FIG. 27 do not take placesimultaneously but rather are governed by clock signals and data inputs(which themselves may be tied to clock signals). This sequentialbehavior is what allows the proper functioning of this cell or buffer(also analogous to a latch in electronic computing). Such behavior iseasy to realize and well-known in electrical implementations, but moreinvolved in a mechanical implementation.

FIG. 28a , comprising the left half, and FIG. 28b , comprising the righthalf, collectively depicts a two cell shift register to illustrate howtwo cells would be connected and to explain how data would move from onecell to the next. In FIG. 28a , cell 1 2801, and in FIG. 28b , cell 22802, are each equivalent to the mechanism depicted in FIG. 25. In FIG.28a , cell 1 2801 has a connection to a clock signal via link 2803(depicted as a partial link to indicate connection to a clock systemthat is not shown), and in FIG. 28b , cell 2 2802 has a connection to aclock signal via link 2806. Links 2804 and 2805 connect the cell 1 2801and cell 2 2802.

Like in FIG. 25, FIG. 26 and FIG. 27, a multi-phase clock signal isassumed to be present, and links 2803 and 2806, and the data inputsassociated with each cell would preferably all operate on differentclock phases, requiring at least a three-phase clock for this particulardesign. The operation of a single cell has already been described, butdemonstrating how cell 1 2801 passes data to cell 2 2802 may beinstructive. The sequence of events is as follows: (1) on clock phase 1,the clock for cell 1 2801 was already at 0, and the data inputs are setfor cell 1 2801. Either the upper or lower lock of cell 1 2801 locks,depending on which input was set to 1; (2) on clock phase 2, the clocksignal for cell 1 2801 is set to 1. This results in the unlocked side ofthe balance present in cell 1 2801 moving, which in turn moves eitherlink 2804 or link 2805. This locks one of cell 2's 2802 holding arealocks, copying the data from cell 1 2801 into cell 2's 2802 holdingarea. Note that the output lock of cell 2 2802 still has not moved; (3)on clock phase 3, the clock signal for cell 2 2802 is set to 1. Thiscopies the data from the holding area locks into cell 2's 2802 outputlock. In detail, one of cell 2's 2802 holding area locks was alreadylocked, so when the clock signal for cell 2 2802 changes from 0 to 1,only the unlocked line could move. When this unlocked line moved, itlocked cell 2's 2802 output lock. It also locked the second of cell 2's2802 two holding area locks; and (4) the clock signal for cell 1 is setto 0. This unwrites cell 1's 2801 data from cell 2 2802 by unlockingonly the cell 2 2802 holding area lock that was originally locked whencell 1's 2801 clock was set to 1, as the other lock was just locked bythe clock signal to cell 2 2802. This cycle then repeats itself as newdata is input into cell 1. In step 2 above, it is noted that the outputlock of cell 2 2802 still has not moved. This allows these exemplaryshift register cells to store previous data, whereas mechanisms such assome of the logic gates described herein have their state completelydetermined by the current data inputs. This is because a cell cancontain not only a previous input (which ends up being shifted to itsoutput lock during clock phase 3), but also the current input, which isstored in the holding area locks.

It will be apparent from this description that if reversibility at theshift register cell (or other mechanism) level is desired, all that needbe done is to run the clock phases in the opposite order. If aretractile cascade is desired, then a scheme like Bennett clocking canbe used, coupled with the appropriate hardware design (e.g., the abilityto store “junk” bits so that no information is lost, allowing thecomputation to be reversible to as many levels deep as desired). In thecurrent example, the shift register being only 2 cells long, only 2numbers can be stored. In an actual system, such a shift register can bearbitrarily long. Further, while this particular implementation is aserial-in/serial-out design, it will be obvious given this example thatMLL can be used to make any other type of shift register desired, suchas parallel-in/parallel-out, serial-in/parallel-out, and others.

Momentum Cancellation

It can be useful to perform computation without altering either thecenter of mass or the moment of inertia of a group of computingstructures, so that the forces that these changes would cause are notcoupled to the overall system, potentially contributing to energydissipation. This can be accomplished by using sets of structures whosemovements cancel out changes in the center of mass or the torque aroundany axis (a “canceling group”). Such techniques can apply to anystructure, such as links, lines, locks, logic gates, balances, clocks,and larger aggregate structures. For example, consider a link or linewhich is used to transmit data from one place to another. Such astructure may be replaced with four parallel structures, conceptuallygrouped as two pairs. Each member of a pair moves in the oppositedirection, canceling changes in the center of mass and linear momentum.However, each pair could still create torque. So, the direction ofmovement of each link is reversed from the first pair to the secondpair, resulting in torque cancellation. Given this type of arrangement,no net force is coupled to the overall device and so such cancelinggroups can be used to transmit data while reducing energy coupled intothe rest of the structure.

FIG. 29 illustrates this concept using groups 2901 and 2902, eachcontaining two members, 2903 and 2904, and 2905 and 2906, respectively.Within a group, each member moves in the opposite direction from theother member (while each member is not connected to the others in thediagram, in an actual system movements would be synchronized, e.g., byclock signals). For example, as depicted, member 2903 has moved to theright, while member 2904 has moved to the left. The accelerations thattake place during these movements will generate forces on the underlyingsupport structure (the anchor block, not shown). Since members 2903 and2904 accelerate in opposite directions, the linear components of theirmomentum will cancel. However, in this arrangement they will stillgenerate a net torque on the anchor block. Adding the second pair ofmembers 2902 containing members 2905 and 2906, which also move inopposite directions within the pair, but generate a torque that isopposite the torque of group 2901, allows complete cancellation.

Obviously, many other designs could be used to either cancel momentum,or reduce the need to do so in the first place (e.g., by reducing mass,or reducing the radii to centers of rotations). Given this, momentumcancellation is not limited to any particular arrangement. Nor arecancelling groups limited to some specific number of members. Even oddnumbers could be used, such as where the members of a canceling group donot have the same masses or momentum. For example, two members could beused to cancel one other member that generates twice the momentum. And,momentum cancellation need not be complete. Additionally, forces alongany axis may be addressed similarly. For example, in actual designs,forces which cause torque along the Z axis, which is defined for thisexample as perpendicular to the figure plane, may also need to becancelled. The complexity and increased mass of complete cancellationmay outweigh the benefits, and the appropriate amount of cancellation(if any), and which force components to cancel, if any, will vary on acase by case basis.

Clocks

In an MLL system, a clock system synchronizes the mechanisms, and alsoprovides force to drive the mechanisms. It is well-known in the field ofcomputer science that computational systems with different numbers ofclock signals (or phases) can be used. At least 2 phases are required,but 3 phases can be advantageous, and higher numbers can also be used.An MLL clock system could consist of one or more clocks which create aplurality of clock signals. These signals could take the form ofreciprocating motion transmitted through the mechanisms, such as vialines, or the use of rigid frames (which are actually just links ofspecialized shape, for example, a rigid frame could connect to a clockat a single location, and then branch out, potentially in multipledirections or dimensions) to connect to many gates or other mechanisms),supported by support links as necessary. The optimal number ofmechanisms connected to a single clock or clock signal will beimplementation-specific, depending on factors like the mass which isbeing driven, the rigidity of the system, and the switching speed.Alternatively, clock signals could be generated by multiple localclocks, such as oscillators or rotating masses, with communicationbetween the clocks as required to keep them synchronized.

Clock signals could be generated in a variety of ways. For example,rotating masses, harmonic oscillators, or cams and cam followers couldall be used, creating periodic motion in links where, for example, oneposition may represent “0” and another position may represent “1”. Arotating mass, which is essentially a flywheel, can serve as a simpleoscillator. Flywheels, coupled to links by rotary joints, could be usedto drive each clock signal back and forth and require no parts beyondlinks and rotary joints. A flywheel could be kept in constant motion bysome sort of energy source or motor, which replenishes the energy lostto dissipative mechanisms in the system. A discussion of exactly howsuch an energy source or motor might be implemented is beyond the boundsof the invention. It is obvious from the literature, which containssubstantial work on both macro-scale motors, and molecular-scale motors,including bio-motors (e.g., ATPases, flagella) and synthetic motors,that there are many ways to implement such motors, and many ways topower such motors, including chemical, light, direct current, andexternal electrical fields.

Other designs for clocks introduce parts beyond links and rotary joints,and so do not technically fall under the definition of MLL. However, asthe use of alternate clocking systems connected to an MLL system mayhave utility, it is described how such alternate clock implementationscan be designed for minimal energy dissipation. Further, since a singleclock can drive many logic elements, even if the clock itself were to besomewhat dissipative, overall, computation could still be quiteefficient.

One alternate clocking system would be to use simple harmonicoscillators, preferably with a high Q factor. The use of simple harmonicoscillators has the advantage that a single clocking frequency would beused, and that the clocking frequency would be provided by a very simplemechanism. Using such an oscillator, components would preferably bedesigned to use sine-like clock signals (including signals withsine-like transitions between 0 and 1 with flat areas in between fortiming purposes), and designed in such a way that they did not generatesignificantly higher frequency overtones during operation (as, forexample, if one moving part collided with another moving part).Alternatively, a sum of simple oscillators could be used, the sumapproximating the desired clock signal. The use of a sufficient numberof oscillators could, in principle, approximate the desired clock signalas accurately as desired, at the expense of additional parts. One way toimplement a harmonic oscillator is with a spring (in which is included aflexure or other structures of similar purpose), which could be made ofany material with the appropriate properties and spring constant,including the same materials as the links.

Cams and cam followers are another way to generate a clock signal. A camand cam follower can be used to generate a very smooth clock signal, asis subsequently described. A cam can also be used to generate a clocksignal with an essentially arbitrary waveform. A cam could be made, forexample, from a rotating link supported by rotary joints at either end.The link thus forms an axle which can be used as a camshaft. The camwould be affixed to the camshaft (or the camshaft could actually be thecam, assuming it has the appropriate cross-sectional shape). A camfollower could be constructed, for example, using a wheel connected totwo rotary joints, connected to a lever arm. Rotating the camshaft wouldrotate the cam. The cam follower wheel would ride up and down on thecam, causing the lever arm to go up and down along with it. The leverarm would be a link in a suitable linkage. Many other geometries andrelative positions for the cam and cam follower could be used, includingdesigns where the cam follower surrounds the cam, or vice versa, such aswith an eccentric rotor and stator, as well as variations in the typesof motion the cam makes, such as designs where the cam simply rocks backand forth, or moves in a manner that is itself under programmaticcontrol, as well as combinations of the foregoing and obviousvariations.

While it may not be obvious how smooth curves can be made at themolecular level, since angles and distances are quantized by the natureof chemical bonds, this issue can be overcome. For example, in diamond,buried Lomer dislocations could be used to create smooth curves on thesurface of a Lonsdaleite (hexagonal diamond) cam. Similarly-gradualchanges could be accomplished with diamond and other materials, by usingchanges in bonding patterns, the incorporation of elements of varyingatomic radii, using strain to slightly displace an atom or atoms, orusing naturally curved structures such a nanotubes. Using thesestrategies, a molecular implementation of cam and cam followers (andindeed, any pieces of such a system) could be made to almost arbitrarilyprecise tolerances, even to distances below a single atomic diameter.

Using a rotating mass to generate clock signals requires only rotaryjoints and links, the basic parts of MLL systems. If a cam and camfollower were used, the rotary joints connecting the cam follower'slever arm to the wheel, and those which allow the cam to rotate, haveagain, already been discussed. However, in a cam-based system, there isrotating contact between the cam and cam follower wheel surfaces, asituation not present when considering the basic parts of MLL. Whilethis may seem like a mechanism that creates undesirable slidingfriction, it need not be. The two surfaces do not have to slide overeach other, but rather rotate synchronously. Analysis indicates that,especially given a molecular-scale, atomically-precise (or nearly so)implementation, the energy dissipation from such a mechanism would bevery low.

In such a molecular-scale mechanism, the very slight distortion in theshape of the wheel and the very slight variation in attractive force(van der Waals) between the surface and the wheel could cause veryslight phonon generation. Viewed in the frame of reference of the camfollower, the wheel and surface would be static other than the very highfrequency shifting of the crystal structures within them. As aconsequence, there should be no generation of low frequency phonons.And, inertia and positional uncertainties caused by thermal noise willprevent the mechanism from being able to reproduce the highest frequencycomponents in the signal on the cam, even in the absence of a low passfilter on the output (which could be used if desired, and could beimplemented, e.g., as a simple spring and mass device).

Also, various cancelation methods could be used to minimize the highfrequency signal component that is encoded on the cam's surface. Thismight be done, for example, by using a plurality of cam follower wheelsthat read a plurality of tracks on the cam surface, each track beingstaggered by some distance. Attaching each cam follower wheel to the camfollower would then effectively sum or average their outputs, cancelingat least some of the high frequency noise signal. Any number of tracksand cam follower wheels could be used, with any desired shape for eachtrack (e.g., different canceling signals could be encoded in eachtrack), resulting in arbitrary accuracy of the aggregate signal. Anothermethod to reduce high frequency noise would be to rotate the crystalaxis of the material from which the cam is made, and perform acorresponding rotation of the crystal structure of the wheel which ismeshing with them. By choosing the crystal rotation and width of the camand cam follower appropriately, other high frequency signals may beeliminated due to the change in timing and atomic spacing as the camcontacts the cam follower wheel. Yet another method of reducing thetransmission of high frequency signals is to reduce the stiffness of thecoupling of the cam and cam follower to the rest of the system. Forexample, reducing the spring constant of the cam follower arm, orreducing the stiffness of the bonds on which the cam follower ismounted, would help filter high frequency signals.

Given these examples, it will be obvious that these are not the onlyways to reduce high frequency components. There are many ways to ensurethat parts in rotating contact do not create or transmit high frequencysignals, and the use of atomically-precise parts in particular allowsthe minimization of such signals. As the cam follower rises and falls onthe curved cam surface, following the clock signal encoded in thatsurface, it will subject the cam surface to inertial forces. Eachacceleration or deceleration of the cam follower will create acorresponding force on the surface of the cam. These periodic forceswill create phonons at the clock frequency. This source of energydissipation can be canceled if two cam followers follow two cams, thetwo cams encoding equal but opposite signals. And, since the clockfrequency is arbitrary, this frequency can be reduced until energydissipation caused by coupling of the high frequency components of theclock signal to mechanical vibrational modes is under desired levels.Note that the cam follower mechanism described can exert a relativelystrong force when the cam is pushing on the cam follower. However,during movement in the opposite direction, the force is limited by thevan der Waals force between the cam and the wheel. This can berectified, if need be, for example, by using two cam followers and twocams (with the encoded signals appropriately rotated with respect toeach other), where the cam followers are on opposite sides of theirrespective cams. The first cam follower can exert a strong force in onedirection, while the second cam follower can exert a strong force in theopposite direction.

Exemplary Switching Time Analysis

The basic constitutive equations of simple Newtonian motion andassumptions about the size and physical strength of links can be appliedto an analysis of the switching time, mass, force, and resonantfrequency for a molecular scale implementation of MLL mechanisms. Toprovide a concrete example, several assumptions must be made, all ofwhich could vary greatly depending on the exact implementation, but theexact performance of a given system is not the point, rather, the goalis to calculate an estimate of one possible operating speed of anexemplary molecular-sized system. Links are assumed to be ˜20 nm inlength and about 0.5 nm to 0.7 nm in diameter. Links are assumed to bemade of diamond or similar material, and to be braced to increase theirstiffness (e.g., a beam with triangular bracing, rather than just astraight beam). The positional difference between “0” and “1” is assumedto be ˜2 nm. Rotary joints are assumed to be like those shown in FIG. 1,and the system is assumed to be operating a room temperature. Theseassumptions allow the calculation of link and rotary joint stiffness. Todetermine the resonant frequency, mass must be determined.

The mass of a typical mechanism can vary widely. Even using a given typeof link, the mass will be quite different depending on whether themechanism is a single 4 bar link, a lock, a balance, a logic gate, etc.,and on the exact implementations of such structures. To use roundfigures, the moving mass of a link might be about 8×10⁻²³ kg, while themoving mass of a mechanism made of several links might be on the orderof 10⁻²¹ kg. Using these assumptions, the resonant frequency for anexemplary molecular-scale mechanism may be around 13 GHz. A square waveclock signal would lead to substantially higher than necessary energydissipation. Therefore, it is assumed that the clock waveform isgenerated as a sinusoidal wave, convolved with a Gaussian to reduceundesirable high frequency components, or optimized using standardlinear systems theory to minimize the generation of undesiredresonances. In addition, to be conservative, the clock can be operatedat a frequency well below the 13 GHz resonant frequency calculated.Depending on various assumptions, such as just how much energydissipation is acceptable, and with how much margin for error, thisresults in switching times in the 1 ns to 10 ns range. Obviously, thisis only exemplary. Larger structures would likely operate at slowerspeeds, while smaller structures, stiffer structures, designs which moveshorter distances between “0” and “1”, lower operating temperatures, orrelaxation of some of the conservative design parameters assumed, wouldresult in faster switching times.

MLL Summary

MLL has been shown to be able to create mechanisms including lines,logic gates, locks, balances, switch gates and shift registers, usingonly rotary joints and links. MLL provides for any combinatorial logicby using various combinations of logic gates which, either alone (e.g.,NAND or Fredkin gates) or in aggregate, are universal. Sequential logic,and therefore memory, can be provided by flip-flops or cells, which canbe combined into shift registers.

Given the availability of both combinatorial logic and sequential logic,it will be obvious that a complete computational system can be builtusing MLL. For example, the Von Neumann architecture, a well-knownTuring-complete architecture, requires three main components: A controlunit, an arithmetic logic unit, and memory. Using combinatorial logicand flip-flops, a finite state machine can be created which can be usedas a control unit. Combinatorial logic can be used to create anarithmetic logic unit. And, flip-flops can be used to create memory.This is all that is needed for a complete computational system. Ofcourse, such a system does not need to be based on the Von Neumannarchitecture; this is simply an example to illustrate the fact that allthe necessary components of a Turing-complete system can be providedusing MLL. Depending on the exact mechanisms used, and the clockingscheme employed, an MLL-based computational system can be irreversible,reversible, or some combination thereof. The ability to createmechanical computing mechanisms, and complete computational systems,using only links and rotary joints can provide advantages which includereduced friction (and therefore power consumption and waste heatgeneration), device design and manufacture simplification, and devicerobustness (e.g., operation at more extreme temperatures than permittedby many other known computational systems, given that mechanical logiccould function up to near the melting point of its constituent parts,whereas, electronic computing suffers from bandgap issues at extremetemperatures).

Mechanical Flexure Logic

Flexures can take the place of the rotary joints used in MLL, resultingin Mechanical Flexure Logic (“MFL”). With the substitution of flexuresfor rotary joints, all MLL mechanisms have analogous MFL mechanisms. Forexample, FIG. 30 shows the MFL version of the MLL lock depicted in FIG.7. Link ends 3001 and 3002 of links 3003 and 3004, respectively, are oneplace where input mechanisms could be connected. Anchored link ends 3007and 3008 of links 3003 and 3004, act in a manner analogous to anchoredrotary joints. Note that there are no actual rotary joints present inthe MFL version of a lock. Rather, flexures, exemplified by thesemi-circular cutouts 3005 and 3006, provide bendable points betweenvarious parts of the structure. These flexures allow force, which may beinput at link ends 3001 or 3002, to be transmitted through triangularlinks 3010 or 3011, respectively, and on to link ends 3012 or 3013(which may be thought of as outputs), respectively. Link 3009 serves thesame purpose as link 709 in the co-planar MLL lock of FIG. 7. The entiremechanism of FIG. 30 can be made (although it need not be) from a singlepiece of material, where the different links are monolithic, butlogically separable because they are bounded by flexures.

Overall, the movement and function of the MFL and MLL locks iscompletely analogous, but changes in the relative angle between links inMFL are facilitated by flexures instead of rotary joints. While locksare used to demonstrate the analogy between MFL and MLL, it will beapparent that the same analogies can be made between any mechanisms, andtherefore by replacing rotary joints with flexures, a Turing-completesystem can be made using MFL. Of course, flexures require suitablematerials, which may differ from that of links, and the geometry offlexures need not be only that depicted in FIG. 30. Flexures arewell-known in the mechanical arts, and suitable designs and materialscould be adapted for almost any degree of motion, size, operatingtemperature, or other parameters.

Mechanical Cable Logic

Another method of implementing computing mechanisms and systems whichare analogous to MLL (and hence also to MFL) is to replace links androtary joints with cables, pulleys, and knobs. This design paradigm willbe referred to as Mechanical Cable Logic (“MCL”). With respect to thebasic parts, or primitives, MCL cables are analogous to MLL links, andMCL pulleys are analogous to MLL rotary joints. Knobs are an additionalprimitive that do not have a direct counterpart in MLL or MFL. Knobs areused to aid in the interaction of cables, for example, to create locks,and in that respect, aid in the building of mechanisms with analogouslogical functions, even if the part itself does not have a directanalog. It will be obvious given the teachings herein, that by applyingforce to a cable, movement can be transmitted down the cable and toother mechanisms as desired (hence their analogy to links). Similarly,it will be apparent that pulleys can be used to, among other purposes,allow bends in cables so that movement can be routed in any directiondesired (hence their analogy to rotary joints).

The MCL primitives can be used to create, among other structures,balances and locks. While MCL implementations of balances and locks maylook different than their MLL counterparts, viewed from a “black box”perspective, MCL balances and locks can be implemented so as to belogically equivalent to the respective mechanisms in MLL. Given this,MCL also provides for Turing-complete systems.

Tracks and Channels

Like MLL rotary joints, MCL pulleys can be anchored or unanchored.However, in MLL links are rigid and this aids in constraining themovement of unanchored rotary joints. In MCL, cables are not rigid, sothe proper geometric constraints need to be provided in a differentmanner. One way to do this would be to keep tension on the appropriatecables (e.g., clock cables) so that pulleys connected to such linescannot move unless, in this example, the clock lines move, in which casepulley movement is constrained to the path the clock cables define.Another way of addressing this issue would be to mount pulleys on linkswhere such constraint was necessary (although another primitive is thenrequired, and since this blurs the distinction between MLL and MCL, suchan embodiment is not addressed further). Yet another way is the use ofchannels, tracks, or other guiding means on the anchor block. By virtueof being affixed in a sliding manner to the guiding means, the motion ofunanchored pulleys are appropriately constrained.

FIG. 31 and FIG. 32 show a top view and side view, respectively, of apulley which can slide in a channel. Anchor block 3101 contains channel3104. Pulley 3102 is monolithic with, or connected to (in a fixed orrotary manner) axle 3103. Axle 3103 connects itself and pulley 3102 tochannel 3104 in a slidable manner. Actuating cable 3105 is affixed toaxle 3103 and enables the movement of the pulley in the channel (e.g.,actuate using a clock line). Note that this is but one way of actuatingand guiding pulley movement, and of affixing a pulley to a track,channel, or other guiding means. Many other designs would be obvious,such a pulley with an axle extending through the anchor block with anexpanded lower part protruding so that it cannot come out of thechannel, a beveled channel and axle (e.g., similar to a dovetail jointin profile) which could accomplish the same goal, or the addition ofanother axle structure on top of the pulley, along with an anotheranchor block, pinning the pulley between the two.

Another way of providing guiding means would be rails mounted on theanchor block, the pulley being affixed to the rails in any one of manyknown means, The point is not the exact mechanical implementation, butrather to provide some guiding means, preferably with low friction, inlight of the flexibility of cables; any of many well-known guiding meanscould be used.

Understanding now how pulley motion can be constrained without the needfor links, the analogies between MLL, MFL, and MCL become easier todescribe. Since it has already been shown that, in MLL, locks andbalances suffice (although they are not the only way) to createTuring-complete systems, it follows that if analogous mechanisms existin MCL, MCL is also capable of being used to create Turing-completesystems. It has already been stated that, with respect to the basicprimitives, MLL links can be likened to MCL cables, and MLL rotaryjoints can be likened to MCL pulleys. To prove this, and show exactlyhow cables and pulleys can be used to create the underlying mechanismsof Turing-complete computing, the design of a lock and a balance isdescribed.

MCL Locks

Locks can be created in MCL using knobs that are integral with, oraffixed to, cables or other structures. With the appropriate design,these knobs allow the reproduction of the features of an MLL lock.Specifically, with respect to a binary embodiment with two inputs, fromthe (0,0) unlocked state, there are two allowable movements, those beingfrom the (0,0) unlocked state to one of the locked states, (0,1) or(1,0). From either of the locked states, the only allowable movement isback to the unlocked state. Note that there is no reason that knobscannot be attached to virtually any structure, as convenient, and theconstruction of locks are not the only use of knobs.

One way to implement the desired logic is depicted in FIG. 33a-c . InFIG. 33a , a first cable 3301 is crossed by a second cable 3302. Twoknobs 3303 and 3304, and 3305 and 3306, respectively, are affixed toeach cable. FIG. 33a shows the lock in the (0,0) position, where eithercable is free to move. FIG. 33b shows the lock in the (0,1) position,the second cable having moved, thus locking the first cable by virtue ofthe fact that one of the second cable's knobs 3305 is between the firstcable's knobs 3303 and 3304, preventing their movement in eitherdirection. FIG. 33c shows the lock in the (1,0) position, the firstcable having moved, thus locking second cable.

Many other designs are possible which allow knobs to act as locks. FIG.34, FIG. 35, FIG. 36, and FIG. 37 depict an exemplary knob design whichcan also enforce the constraint that the only allowed movement in a lockfrom the (0,1) or (1,0) state is to (0,0). This knob design is morecomplex, but requires only two knobs (one on each cable) instead offour, to create the desired lock logic.

FIG. 34 shows a single knob 3401. Generally a cable would be attached toeither end (not shown), but such knobs could be used in other scenariosas well, such as connected to MLL links.

FIG. 35 shows how two such knobs 3501 and 3502, mesh with each other toform a lock. In this figure, the lock is shown in the blank state(meaning, neither knob is positioned to block the movement of theother).

FIG. 36 and FIG. 37 depict the same knobs 3501 and 3502 in the (0,1) and(1,0) state (or vice versa; since the mechanism is symmetric, the knobthat is defined as the 0 knob and that which is defined as the 1 knob isarbitrary).

It can be seen by inspecting the shape of these knobs and their relativepositions in the blank, (0,1), and (1,0) states that if two cables orother structures interact via the appropriate movement of such knobs,that constraint that the only movement allowed from the (0,1) or (1,0)state is to the (0,0) state, is enforced.

MCL Ovals

Conceptually, it can be useful to define a structure in MCL called an“oval” since this arrangement of basic parts is one way to create morecomplex mechanisms such as balances and shift registers.

As depicted in FIG. 39, one way to implement an oval uses a closed loopof cable 3801 (referred to as the “logic cable” to distinguish it fromcables serving as inputs/outputs, including those providing clocksignals, although this distinction is for clarity of description only,since logic cables can also provide input/output, as in the case ofcrossed ovals which can be used to form cells and shift registers),which may include one or more structures such as knob 3802, and whichgoes around one or more pulleys such as pulley 3803 (two pulleys aredepicted but other numbers could be used to change the shape, length,vibrational and entropic characteristics, or other characteristics ofthe oval, which despite the name, need not be oval in shape). If one ormore of the pulleys can be unanchored, guiding means such as track 3804may be included. Unanchored pulleys may be actuated (moved along theirguiding means) by cable 3805, which may be, e.g., tied to a clocksignal.

One or more cable housings such as that exemplified by housing 3806 maybe included to reduce energy loss, as described elsewhere herein. Knobsfacilitate interaction with other structures and may be connected to oneor more input/output cables 3807 and 3808. By itself and in its simplestform, an oval merely takes an input and may (but does not have to), passit on as an output. For example, if cable 3807 moves and the pulleys areanchored, the opposite side of the logic cable must also move, causingthe movement of cable 3808. Thus, the oval may relay data, but nosubstantial computation is taking place. However, ovals can be designedto carry out computations by interacting with other structures(including, e.g., other ovals, or cables). When coupled with locks, thisis one way to construct a balance via MCL.

MCL Balances

FIG. 39 depicts a balance as part of an oval. Balances and ovals canalso serve as part of a shift register. The balance includes pulley 3902and the left part of logic cable 3901. FIG. 39 depicts an oval withunanchored pulleys and two crossed cables which provide data input, thetwo crossed cables coming from, e.g., data cables, or another oval.Optional structures such as cable housings are omitted for clarity, andas usual, an anchor block is assumed to be present, but not depicted.Logic cable 3901 goes around pulley 3902 (and its mate, unlabeled). Bothpulleys are mounted on tracks, exemplified by 3903. Clock line 3904actuates the mechanism by pulling on the pulleys, which will cause themto slide in their tracks. The logic cable has two pairs of knobs 3905and 3906, and 3907 and 3908. Cables 0 3909 and cable 1 3910 provideinput to the oval. Each crossed cable has a pair of knobs 3911 and 3912,and 3913 and 3914, respectively. By crossing the oval (at right anglesin this diagram, but other angles and designs can be used), cables 0 and1 can position their knobs to interact with the knobs of the oval.Triangular knobs 3915 and 3916 (shown as triangular only to visuallydistinguish them from the other knobs; this shape is not significant)are connected to the 1 output line 3917, and the 0 output line 3918,respectively. This configuration is just exemplary. The output linescould just as easily be, e.g., positioned differently, or connected tothe appropriate lock knobs rather than using separate knobs.

FIG. 39, FIG. 40, and FIG. 41 differ only in the position of the inputcable knobs. In FIG. 39, both locks are in the blank position; meaningthat the input cable knobs and the logic cable knobs would not interactif the mechanism were actuated. In FIG. 40, cable 3909 has moved knobs3911 and 3912 so that knob 3911 is now between two of the knobs on thelogic cable, 3905 and 3906. This can be considered an input of 0, sincethe zero input line has moved. If the mechanism were actuated in thisstate, the upper side of the oval would be prohibited from moving, asknobs 3905, 3906, 3911 and 3912 form a lock which is then locked.

In FIG. 41, cable 3909 has not moved, but instead cable 3910 has moved.This can be considered an input of 1, since the 1 cable has moved. Theeffect is to lock the opposite side of the oval by placing knob 3913between knobs 3907 and 3908. This locking of one side or the other of anoval is analogous to locking one side or the other of the appropriatelink in an MLL balance. The functioning of the oval-based balance is asfollows: Assume that the starting position of the pulleys is at the leftside of their respective tracks. When the inputs are set, the inputcables lock either the upper or lower side of the oval. The clock linethen moves the pulleys from the left to the right. The lateral movementof the pulleys is the same regardless of the inputs. However, the sideof the logic cable that moves is determined by the inputs. Whicheverside of the logic cable is locked is forced to remain stationary.Therefore, when the pulleys move, only the unlocked side of the logiccable moves. This results in the movement of the 0 output line if aninput of 0 was provided, and movement of the 1 output line if an inputof 1 was provided.

FIG. 42 shows the position of the mechanism assuming that an input of 1was provided and then the clock line moved the pulleys to the right.Since knob 3913 had moved between knobs 3907 and 3908, the lower side ofthe oval was locked. Therefore, when the pulleys move to the right, thelogic cable must follow in the only manner possible: by rolling thelogic cable so that knob 3915, and thus the 1 output line 3917, moves tothe right. Note that data cables such as 3909 and 3910 are not the onlymanner of providing input to an oval, and output cables such as 3917 and3918 are not the only way of obtaining output from an oval. For example,crossed ovals can interact directly, the logic cable of one oval servingas an input to a neighboring oval. Given that, when coupled with locks,input can be used to control which side of an oval moves, this isanalogous to the functioning of an MLL or MFL balance. And, sinceTuring-complete systems were shown to be possible using only locks andbalances in MLL, it follows that MCL can also implement Turing-completesystems.

Moving Mass

One advantage to some MCL embodiments is reduced moving mass as comparedto some embodiments of MLL or MFL. Because cables are not required to berigid, they can have a smaller cross section and correspondingly lowermass than MLL links of equivalent length. A conventional example of thisprinciple is to compare the mass of a cable with the mass of a beam-likestructure. In general, a structure which only has to withstand tensileforces can be made less massive than a structure which must alsowithstand, e.g., compressive or bending forces. At the molecular scale,examples of strong but flexible structures which might be used as cableinclude carbyne (linear acetylenic carbon), polyacenes, polyethylene,and polyiceanes, although many other structures could be used.

A potential disadvantage to the use of cables is that the flexibilitycan allow vibrational modes that would not exist in a stiffer structure.Further, these vibrational modes may change as the length of a givensection of cable changes. For example, if the distance between twopulleys changes, changing the length of the cable segment between them,the allowed vibrational modes may change, just like fretting a guitarstring at different positions. This also results in entropic changes tothe system. Either of these effects can lead to energy dissipation.

However, these vibrational and entropic issues can be addressed whilestill keeping the moving mass of the mechanisms low. This can beaccomplished by constraining cables in such as manner as to prevent themfrom being free to vibrate. One embodiment of this concept would be tohave cables lie in trenches in the anchor block. Such trenches, ifthought of as having a rectangular cross section (though this need notbe the case) would constrain the cable on three sides, with the fourthside being open to facilitate routing the cable out of the trench tointeract with pulleys. It is also possible to constrain a cable on allsides, such as the way a Bowden wraps its inner cable in a sheath orhousing. If this sheath is relatively rigid, and the internal space ofthe sheath appropriately sized as compared to the cable, essentially novibration will be permitted within the sheath. A molecular example ofthis would be a polyyne cable in a (9,0) SWNT (single-walled nanotube),but obviously many structures could be used, preferably those which arerigid, closely fit the cable and the sheath, and which allow the cableto slide freely in the sheath (but not to vibrate substantially).

While short segments of cable may be exposed between trenches, sheaths,or other types of housings, and where the cable contacts a pulley, thesesegments will be relatively short compared to overall cable length,marginalizing the energy loss from cable vibrations and entropicchanges. Since the cable housings need not move with the cable, movingmass is kept low, potentially allowing systems with higher switchingfrequencies as compared to systems that require more massive rigid linksinstead of flexible cables.

Also, a cable system could be implemented with fluids inside housings. Asolid plug at one end of the housing would push on the fluid, which inturn pushes on another plug at the opposite end of the housing. Like aclosed loop of cable, by actuating at either end, this can effectivelyprovide a “cable” (though made of a fluid, which includes a gas) whichcan be pushed or pulled on by actuating the appropriate end. Suchdesigns could also be used to implement balances and locks, moving theparts hydraulically rather than via a solid link or cable. While ahydraulic system would not traditionally be called a cable, it isconsidered to be a cable system herein as the logical and mechanicalfunctioning is almost identical to that of a solid cable.

Type 1-4 Systems

As mentioned previously, due to the use of ratchets and pawls, detents,springs, or other mechanisms which store and then release potentialenergy in a manner not directly tied to the systems' computationaldegrees of freedom, all pre-existing Turing-complete systems formechanical computing can be categorized as Type 1. Due to possibleenergy savings, all other things being equal, Type 2-4 systems would bepreferred over Type 1 systems, with Type 4 systems being most preferred.MLL, MFL, and MCL are all capable of creating Type 2-4 systems. In fact,most of the embodiments described herein would result in Type 4 systems,while adding, e.g., springs to some mechanisms (such as between thegradual lock depicted in FIG. 9 and other mechanisms, to permitbacklash) could result in a Type 2 system, and some designs which, e.g.,could leave locks in the (0,0) state with some non-trivial frequencycould result in a Type 3 system (although this can be avoided withproper design; locks being in the (0,0) state need not mean that partsare free to move, as can be seen in the mechanism described herein).

It may not be immediately apparent that MFL can be used to create Type3-4 systems, as flexures may seem to store potential energy by theirvery nature. Indeed, some flexure-based designs, if using the flexuresto store potential energy and then release it to some effect on thesystem, would be categorized as Type 1 or Type 2. However, in MFL,flexures need not be used for potential energy storage. Rather, theirfunction can be solely to provide kinematic restraint, just as theanalogous structure in MLL, the rotary joint, does. As such, the forceneeded to bend a flexure can be arbitrarily small as long as the flexurestill provides the necessary rigidity with respect to the relevantdegrees of freedom. This leads to the conclusion that the potentialenergy storage of flexures can be trivial, just like the potentialenergy stored in the stretching of MCL cables, or the stretching,bending, or compression of MLL links.

Further, even if the force required to bend a flexure were substantial,since flexures are not being using to actuate movement in a Type 3-4system, systems can be designed where the net potential energy of theflexures is essentially 0. For example, a pair of flexures connected toa link could be pre-stressed in opposite directions. The movement of thelink in one direction would increase the potential energy of one of theflexures, while decreasing the potential energy of the other flexure,resulting in no net change (and therefore no net increase in the forcerequired to move the link) over some allowed range of motion.

Summary

Three exemplary paradigms for mechanical computing, MLL, MFL, and MCL,have been described. Each of these paradigms are capable of providingboth the combinatorial logic and the sequential logic required to createa Turing-complete computational system. Each design paradigm also allowsfor reversible computing, and simulations of a molecular-scale mechanismindicate that properly designed embodiments of MLL can compute withlevels of energy dissipation under the Landauer Limit. There is noreason to think that MFL and MCL cannot provide similar efficiency.

Four classes of computing systems have been described, designated Types1-4. Type 1 systems have the lowest ultimate potential for energyefficiency, and are the only type of computational system previouslyenabled. MLL, MFL, and MCL share physical and logical parallels, in somesense being three embodiments of the same concepts. Each is capable notonly of Turing-complete computing, but also of providing Type 2, Type 3,and Type 4 systems (alone, or in combination with each other), allowingfor decreased energy dissipation. Each also has a very low number oftypes of required primitives, with MLL and MFL only requiring two basicparts, and MCL requiring three, reducing the complexity of systemdesign, manufacture, and assembly. Further, not only are a very smallnumber of basic parts required, but none of the basic parts includegears, ratchets and pawls, detents, or many other common mechanisms thatare widely used in other systems, but which are likely to dissipateexcessive energy through friction or vibration. Finally, each arecapable are creating computational systems which use dry switching; nopower need be wasted by applying force to a basic part or mechanism,only to find that it will not move due to its logical state.

Given the teachings herein, including multiple embodiments thatdemonstrate the overarching design principles of being able to provideTuring-complete computing, reversible if desired, via Type 2-4 systems,with very few types of primitives, which lend themselves to the creationof energy-efficient mechanisms, both due to the nature of the mechanismsthemselves, and because such mechanisms and systems can be designed touse dry switching, it will be apparent that variations using differentmechanisms or primitives could be created, and it is the high-leveldesign paradigms, not the specific embodiments, which should be seen asthe boundaries of the invention.

1. A computing mechanism comprising: an anchor block; and a plurality oflogic structures mounted to said anchor block, each of said logicstructures having an arrangement of primitives selected from the groupconsisting of rigid links, pulleys, cables, and knobs, and being movablyconnected to said anchor block by joints selected from the groupconsisting of rotary joints and flexures, each of said logic structuresbeing configured to define a position of at least one output based on alogic operation performed on at least one input, where the logicoperation includes at least one of a combinatorial logic function or asequential logic function, wherein said logic structures are connectedtogether such that outputs from one subset of logic structures serve todefine the inputs of another subset of logic structures.
 2. Thecomputing mechanism of claim 1 wherein each of said logic structuresfurther comprises: one or more moveable input primitives that providesaid inputs and one or more moveable output primitives that provide saidoutputs, wherein discrete positions of said input and output primitivesrepresent integer values; and internal connecting primitives arranged toconnect said input primitives to said output primitives such that thepositions of at least a subset of said output primitives are defined bya logic operation of at least a subset of said input primitives.
 3. Thecomputing mechanism of claim 1 wherein at least a subset of said logicstructures are configured such that the pattern of connection betweenprimitives in such logic structures remains constant as they operate. 4.The computing mechanism of claim 1 operated by a clock, wherein at leasta subset of said logic structures are configured such that non-trivialstorage and release of potential energy resulting from operation onlyoccurs at a speed imposed by the clock.
 5. The computing mechanism ofclaim 1 wherein at least a subset of said logic structures areconfigured such that they do not require storage or release ofnon-trivial amounts of potential energy as they operate.
 6. Thecomputing mechanism of claim 1 wherein at least a subset of said logicstructures are configured to provide reversible logic gates.
 7. Thecomputing mechanism of claim 1 wherein at least a subset of said logicstructures are configured such that operation does not requiretransmitting force to any part that is not free to move responsive tosuch force.
 8. The computing mechanism of claim 7 wherein at least asubset of said logic mechanisms structures are each constructed from aplurality of locks and balances connected so as to perform a desiredoperation, each balance having a movable balance actuating element and aplurality of movable balance driven elements which move when saidbalance actuating element moves, unless blocked from such movement, andsaid locks being connected to said balance driven elements andconfigured such that the positions of lock input elements determinewhich of said balance driven elements are blocked from moving when saidbalance actuating element moves.
 9. A computing mechanism operated by aclock and comprising: an anchor block; and a plurality of logicstructures mounted to said anchor block, each of said logic structuresbeing configured to define a position of at least one output based on alogic operation performed on at least one input, where the logicoperation includes at least one of a combinatorial logic function and asequential logic function, and being configured such that the pattern ofconnection between primitives remains constant as said logic structureoperates, wherein said logic structures are connected together such thatoutputs from one subset of logic structures serve to define the inputsof another subset of logic structures, further wherein at least a subsetof said logic structures are configured such that non-trivial storageand release of potential energy resulting from operation only occurs ata speed imposed by the clock.
 10. The computing mechanism of claim 9wherein each of said logic structures further comprises: one or moremoveable input primitives that provide said inputs and one or moremoveable output primitives that provide said outputs, wherein discretepositions of said input and output primitives represent integer values;and internal connecting primitives arranged to connect said inputprimitives to said output primitives such that the positions of at leasta subset of said output primitives are defined by a logic operation ofat least a subset of said input primitives.
 11. The computing mechanismof claim 9 wherein at least a subset of said logic structures areconfigured such that they do not require storage or release ofnon-trivial amounts of potential energy as they operate.
 12. Thecomputing mechanism of claim 9 wherein at least a subset of said logicstructures are configured to provide reversible logic gates.
 13. Thecomputing mechanism of claim 9 wherein at least a subset of said logicstructures are configured such that operation does not requiretransmitting force to any part that is not free to move responsive tosuch force.
 14. The computing mechanism of claim 13 wherein at least asubset of said logic mechanisms structures are each constructed from aplurality of locks and balances connected so as to perform a desiredoperation, each balance having a movable balance actuating element and aplurality of movable balance driven elements which move when saidbalance actuating element moves, unless blocked from such movement, andsaid locks being connected to said balance driven elements andconfigured such that the positions of lock input elements determinewhich of said balance driven elements are blocked from moving when saidbalance actuating element moves.
 15. A computing mechanism comprising:an anchor block; and a plurality of logic structures mounted to saidanchor block, each of said logic structures being configured to define aposition of at least one output based on a logic operation performed onat least one input, where the logic operation includes at least one of acombinatorial logic function and a sequential logic function, whereinsaid logic structures are connected together such that outputs from onesubset of logic structures serve to define the inputs of another subsetof logic structures, further wherein at least a subset of said logicstructures are configured such that they do not require storage orrelease of non-trivial amounts of potential energy as they operate. 16.The computing mechanism of claim 15 wherein each of said logicstructures further comprises: one or more moveable input primitives thatprovide said inputs and one or more moveable output primitives thatprovide said outputs, wherein discrete positions of said input andoutput primitives represent integer values; and internal connectingprimitives arranged to connect said input primitives to said outputprimitives such that the positions of at least a subset of said outputprimitives are defined by a logic operation of at least a subset of saidinput primitives.
 17. The computing mechanism of claim 15 wherein atleast a subset of said logic structures are configured to providereversible logic gates.
 18. The computing mechanism of claim 15 whereinat least a subset of said logic structures are configured such thatoperation does not require transmitting force to any part that is notfree to move responsive to such force.
 19. The computing mechanism ofclaim 18 wherein at least a subset of said logic mechanisms structuresare each constructed from a plurality of locks and balances connected soas to perform a desired operation, each balance having a movable balanceactuating element and a plurality of movable balance driven elementswhich move when said balance actuating element moves, unless blockedfrom such movement, and said locks being connected to said balancedriven elements and configured such that the positions of lock inputelements determine which of said balance driven elements are blockedfrom moving when said balance actuating element moves.
 20. A computingmechanism comprising: an anchor block; and a plurality of logicstructures mounted to said anchor block, each of said logic structuresbeing configured to define a position of at least one output based on alogic operation performed on at least one input, where the logicoperation includes at least one of a combinatorial logic function and asequential logic function, said logic structures each being constructedfrom a plurality of locks and balances connected so as to perform saidoperation, each balance having a movable balance actuating element and aplurality of movable balance driven elements which move when saidbalance actuating element moves, unless blocked from such movement, andsaid locks being connected to said balance driven elements andconfigured such that the positions of lock input elements determinewhich of said balance driven elements are blocked from moving when saidbalance actuating element moves, wherein said logic structures areconnected together such that outputs from one subset of logic structuresserve to define the inputs of another subset of logic structures. 21.The computing mechanism of claim 20 wherein at least a subset of saidlogic structures are configured to provide reversible logic gates.